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Dynamic C Applications framework

1. down init 7 1 2100 2200 LCD has two lines of 20 characters the standard version Other versions are available An underline cursor may be positioned under any character The five key system uses the costatement programming paradigm and runs under the simplified real time kernel There also is an old system library 5 LIB that requires the real time kernel The 5KEY LIB library is described in Appendix B The five key system provides a simple scheme for changing operating parameters It is possible to cycle through a number of menus by pressing the MENU key For each menu a number of items may be selected by pressing the ITEM key Each item may have one or more fields each of which is selected by pressing the FIELD key When the desired parameter is selected adjust the parameter by pressing the UP or DOWN keys These keys cycle forward or backward through a list of acceptable values It is not possible to select a wrong value In addition to the five keys the HELP key provides help in context for each specific menu item The keys F1 F2 F3 F4 del and add can each be programmed for a specific task Operator Features The five key system allows an operator to do the following tasks Update parameters using the five ITEM FIELD UP and DOWN Parameters can be of several types string float in
2. 68 serial outputs 68 69 software support 66 67 RS 485 communication 76 77 78 81 disabling driver 78 73 serial outputs 76 77 two wire network connections 76 real time kernel 17 39 42 43 48 70 88 RER DIB o 44 RIS ee 67 68 run after 46 Ec 46 run cancel sss 46 run every 44 45 46 47 48 RUNKERNEL 39 42 43 44 72 PUN WAtCD onse nde 49 Index 99 sample programs communication 69 Five Key system 59 master slaves 79 80 81 real time kernel RTK 49 SCC aie r 64 66 70 22 242 77 SERO VBG uoa 67 serial communication 64 67 76 77 78 81 master slave 77 78 serial transmission 68 69 terminating 22 22 0422 69 SCUMP eerte ht ERES 34 shared variables 14 15 18 identifying usus 18 multitasking 17 18 simplified real time kernel SRTK 17 39 42 43 57 88 sample program 42 iterari 64 66 slave response format 76 78 Smart Modem Hayes 5 ies attese 65 70 software support RS 232 67 SRTK simplified real time kernel 17 SRTK EIB eire 42 srtk hightask
3. Call user defined FASTCALL function if user specified number of ticks have occurred Service second timer Hit the hardware watchdog and virtual watchdogs RTK or SRTK defined Call RTK or SRTK Figure 4 1 Operation of Virtual Driver at Various Clock Interrupts 38 The Virtual Driver Dynamic C 32 v 6 x Calling Sequence To enable or disable the various services of the virtual driver include define parameters before calling the virtual driver initialization function VdInit The examples below illustrate how to do this tasks For only no default define NTASKS nn max of virtual watchdog timers default 10 define WATCHDOG nn load and run RTK or SRTK default off define RUNKERNEL state 1 true 0 off load fastcall but don t run it define VD_FASTCALL state 1 load 0 don t load initialize the virtual driver default off VdInit Init fastcall to be called every nn 0 255 clock interrupts It s off nn 0 by default Must be called after VdInit vd initquickloop nn The RTK Driver If define RUNKERNEL 1 is defined in a program that uses the virtual driver the function will call the real time kernel RTK or simplified real time kernel SRTK every 25 milliseconds To use a real time kernel the program must use LIB or SRTK LIB The Fastcall Driver If the virtual driver is ac
4. 33 example sss 34 network connections two wire RS 485 76 ninth bit address protocol 76 ninth bit binary communication 77 78 nonmaskable interrupt 52 NO CARRIER 65 nodebug 222 48 nonmaskable interrupt NMI 52 NTASKS 39 44 number of bits 67 old Five Key system 92 alarm functions 92 changing parameters 90 code driven 88 90 data 90 function 91 HELP key 91 linked list driven 89 monitoring data 91 monitoring parameters 90 string messages 9 time and d te ig 9 Op init zT 77 78 Zl aas 78 op send 21 78 opto 22 binary protocol 76 77 78 79 Dynamic C 32 v 6 x optodelay 78 RS 232 68 69 5 485 2 76 77 Parity 67 phy 71 PECBUS taies 72 PLU Program Loader Utility 72 preemption 16 17 18 with 39 preemptive multitasking
5. 56 WR a Suus dette 56 88 fk helpmsg 59 fk alpha 60 fk 61 fk item int i e 60 fk item 60 fk item settime 60 fk item uint 60 fk monitorkeypad 57 59 59 flash 53 Application Frameworks G BelCIO 73 edet 46 global initialization 40 initializing CoData 24 granularity 39 costatement 31 hardware watchdog 52 Hayes Smart Modem 65 70 71 HELP 56 57 91 identifying shared variables 18 init kernel 46 Init Olaus ee ROI 25 init srtkernel ususs 42 initialization receive buffer 67 transmit buffer 67 Z180 Port 1 77 initiation serial transmission 68 69 78 input RS 232 5 ntes 68 72 73 73 interrupt driven transmission 78 interrupts essent 14 18 HINT VEC 67 disabling 222 22 73 latency voice 15 CAUSES ugar 14 NESE RSS 15 routines 15 SERO VEC acte 67 67 service
6. 42 srtk lowtask sssss 42 stack corruption checking 47 48 state machine 23 222 22 Stop DiIts zi 67 string messages in the Five Key system 91 S per Tesetz euer 53 suspend 17 45 46 47 48 49 70 72 78 syntax costatement 25 100 Index T TASKSTORE SIZE 47 48 time and date in the old Five Key system 91 timer watchdog 40 52 timers BRE tet tee 73 transmission initiating 68 69 78 interrupt driven 78 transmit buffer 69 78 initialization 67 writing essere 68 69 two wire connections RS 485 network 76 U WARD ease rens 72 56 init initialize CoData structures 24 uploading 70 SERERE 47 V VD FASTCALL 39 vd initquickloop 39 vd quick loop 39 VdGetFreeWd 40 ee amete 38 39 40 and waitfor delay functions 29 initialize CoData structures 24 VdReleaseWd 40 VDRIVER LIB 38 VdWdogHtit 40 virtual driver 37 43
7. Setting the start field does not actually cause the costate ment to execute This simply means that the costatement is active and is ready to execute The calling program s execution thread must pass through the costatement However this code works when only one task can request the costatement atatime If several tasks request the execution of a costatement at the same time the costatement will certainly execute once maybe twice In general each of the multiple requesters is not guaranteed a separate execution of the costatement Request the execution of a costatement in the following cases The requester and requestee are in different tasks where one preempts the other so direct calls are out of the question Multiple costatements must start simultaneously something that cannot be done with a direct call One task needs to start another but no further synchronization is needed between the tasks 32 Costatements Dynamic C 32 v 6 x Nesting Costatements If a costatement needs to run another costatement as a subtask where the original task cannot proceed until the subtask has completed a direct call using a waitfor 15 probably the best way to accomplish the desired end This is done by placing the subordinate costatement in a C function that returns 0 on each pass of the execution thread except the last pass when completion occurs at which time it returns 1 Upper level call within a costatement costat
8. Software Support essen 66 RS 232 Sottwate 67 XMODEM 70 Miscellaneous Functions sese 71 RS 485 Drivets NER OR e Ses 73 Labraries de itas eddie 73 Sample Programs sse 74 Chapter 9 Master Slave Networking 75 Communication Protocol sssssssseseeeeneeennnenes 76 Hardware Connection ote p caine delaware 76 Software Support eee 77 Miscellaneous Functions 78 Libraries and Sample Programs serere 81 Libraries e RR RA n 81 Sample Programs iscir a o a aiis 81 Appendix A Execution Speed 83 Appendix B Old 5 Key System 87 Code Driven Approach 88 Linked List Approach ert ete tetto 89 Updating and Monitoring Parameters 2 90 Monitoring Function Keys essere nennen 9 Monitoring Help Keys 9 Periodic Display RR ROSE RE GNRERGR 9 Software Alarms sese 92 5 Key Support Functions 92 Index 95 Application Frameworks Table of Contents v vi Table of Contents Dynamic C 32 v 6 x Tuis MANUAL Z World customers develop software for their programmable controllers using Z World s Dynamic C 32 development system running on an IBM compatible PC The controller is connected to a CO
9. suspend 10 motor OFF The first call to suspend stops the program from executing for the number of ticks in the argument five ticks or 0 1 second The first while loop causes the program to suspend repeatedly for 0 1 second until the valve is no longer closed The suspend time allows the time precision for detecting the event to be specified The second while loop causes the program to suspend repeatedly for 0 1 second until the valve closes The additional suspend 10 after the motor closes ensures that the motor continues to run for ten ticks 0 2 seconds to close the valve tightly Application Frameworks Real Time Kernels 45 The above routine could also be made into an endless loop In that case it would be invoked one time by a call such as request task4 at initialization It would time its own progress by means of calls to suspend inserted in the code Kernel Functions The following routines control the activity of the RTK void run at int tasknum void time Requests the kernel to run the task specified by tasknum when the time 1 greater than equal to the time specified by the pointer time The time pointer points to a 48 bit number stored least significant byte first which is the number of ticks since init kernel was called int comp48 void timel void time2 Compares two 48 bit time values The function returns for timel lt time2 0 for timel time2 and 1 timel g
10. 1 MODIFY 10 90 Old 5 Key System Dynamic C 32 v 6 x Linked List Approach The two variables previously mentioned Tb and time would be added to the linked list with the following calls 5key setmenu Menul Tb 5key Fdata amp Tb 300 00 100 00 Tb help sizeof Tb help RTCLK MODIFY 10 NO DISPLAY 5key setmenu Menul time 5key Tdata time 0 0 0 0 time help sizeof time help RTCLK MODIFY 10 NO DISPLAY Monitoring Function Keys The five key system monitors the function keys F1 F2 and F4 Programmers may write functions that correspond to each function key Load function key handlers using the procedure 5key setfunc For example with the call 5key setfunc testl test2 NO FUNCTION testl function test1 is executed whenever F1 or F4 1 pressed Function test2 is executed whenever F2 is pressed Pressing F3 will not cause anything to happen Function key service routines can control the display and the keypad Monitoring Help Keys An item specific help message can be displayed when the HELP key is pressed If no help message 15 needed a call like the following will disable help messages _5key float Tb amp Tb 300 00 100 00 NO HELP 0 MODIFY 10 Periodic Display When there is no keypad and no display activity for 1000 ticks 25 seconds the five key system will display the time date up to 10 messages and up to 10 linked list parameters The time and date
11. 70 Dxmodem 70 70 Dynamic C Function Reference 89 programming port 72 070 circ int 72 DzOmodem chk 72 DzOsend prompt 69 E echo option 67 EEPROM eee 53 72 CMTOL CXILS 33 use of setjmp longjmp 34 ERROR 52 EXCEPTION 242 52 Dynamic 32 v 6 x execution speed other operations 85 expression evaluation and costatements 35 F Ely E25 sns 56 57 failure detection and recovery 54 hardware failures 52 hardware watchdog 52 power failure 52 protected variables 54 TeSeL ciere 53 software failures 52 super 53 fastcall 17 38 39 42 FIELD 222 56 firsttime iones 27 28 28 FONCHONS nee 28 Calling 2 5 28 definition of 28 Five Key system 55 56 63 75 DOWN 56 extending 22222 4 2 4 57 FIELD 2 242402 56 HELP Key ne 56 57 ITEM 222 56 linked list driven 9 MENU 56 operation
12. baud the baud rate in multiples of 1200 for example specify 8 for 9600 baud modem If 1 modem is supported If 0 no modem echo every character is echoed If 0 no echo If CTS RTS handshaking is selected transmission from the sender is disabled by raising RTS when the receive buffer is 8096 full The software lowers RTS enabling the sender to transmit when the receive buffer falls below 2096 of capacity In a similar manner a remote system can prevent transmission of data by Z180 Port 0 by asserting its RTS connected to the Z180 Port 0 CTS e void zObinaryset Puts the serial receiver in BINARY mode This means that all received characters are placed in the receive buffer e void z0binaryreset Places the serial receiver in ASCII mode where the BACKSPACE character 0x08 is parsed out of the receive buffer Character echo also resumes if it was selected int Dread zOlch char ch Reads a character from the receive buffer into character ch The function returns 0 buffer is empty 1 byte has been successfully extracted from buffer e int Dwrite zOlch char ch Places a character in the transmit buffer If not already transmitting the function initiates transmission It returns 0 transmit buffer did not have space for ch 1 write was successful int Dread 20 char buffer char terminate Checks the receive buffer for a message terminated with the character terminate The message is c
13. 78 computing 73 D DATA mode 65 Ddelay 100ms 72 deciphering modem commands 71 DEE key est 57 delay modem communications 72 delay functions 29 delay 72 DelayMs 27 28 36 38 43 DelaySec 27 38 43 DelayTicks 27 38 39 43 DELETE key 56 DEMO 49 Dget modem command 71 96 Index Dinit com2 1 22 66 Dinit 70 Dinit 66 22222 66 66 disabling interrupts 73 DMA channels 73 Z180 Serial Channels 0 and 1 73 disabling the RS 485 driver 78 Dkill z tenti 69 DMA channels disabling interrupts 73 DOWN 56 downloading e 70 programs 72 70 Dread 270 2 2222 20 68 Dread zOlch 68 20 69 Dreset 200 69 Drestart z modem 72 Dscasend prompt 70 Dwrite sca sese 70 20 eni 69 _701 68 Dxmodem z0down
14. Alarm 4 has no function Nothing will happen when Alarm 4 signals 5 Key Support Functions The functions listed here may be used to develop a menu system specific RY These functions are described in the Dynamic C Function Reference manual to an application Some of the functions for example 5key float return an integer representing one of the keys MENU ITEM UP DOWN ADD or DE LETE These integers are also defined as symbolic constants in 5KEY LIB These functions return such a value to indicate that the particular key has been pressed They return 1 when no key has been pressed or the value is being monitored When data are monitored they are presumed to be changed somewhere else in the program The PK2100 display reflects the change when monitored data changes 92 Old 5 Key System Dynamic C 32 v 6 x The following list groups the five key functions Initialization Functions 5key setmenu 5key setalarm 5key setfunc 5key setmsg Five Key Service Functions _5key float _5key integer _5key boolean _5key time _5key date 5key menu 5key boolean Extended Five Key Service Functions 5key 12out 5key uinput _5key diginput 5key dacout Miscellaneous Functions lcd server _5keysettime _5keysetdate _5keygettime _5keygetdate 5key init menu Application Frameworks Old 5 Key System 93 94 Old 5 System Dynamic 32 v 6 x Symbols suce 39 43 FINT VEC use
15. GY The C Programming Language by Kernighan and Ritchie C A Reference Manual by Harbison and Steel e Knowledge of basic Z180 assembly language and architecture For documentation from Zilog refer to the following texts GY Z180 MPU User s Manual Z180 Serial Communication Controllers Z80 Microprocessor Family User s Manual Acronyms Table 1 lists the acronyms that may be used in this manual Acronym EPROM EEPROM LCD LED NMI PIO PRT RAM RTC SIB SRAM UART Table 1 Acronyms Erasable Programmable Read Only Memory Electronically Erasable Programmable Read Only Memory Liquid Crystal Display Light Emitting Diode Nonmaskable Interrupt Parallel Input Output Circuit Individually Programmable Input Output Programmable Reload Timer Random Access Memory Real Time Clock Serial Interface Board Static Random Access Memory Universal Asynchronous Receiver Transmitter viii About This Manual Dynamic C 32 v 6 x Icons Table 2 displays and defines icons that may be used in this manual Table 2 Icons Icon Meaning Icon Meaning Refer to or see Caution A High Voltage Factory Default Please contact Ti p Tip Conventions Table 3 lists and defines typographic conventions that may be used in this manual Table 3 Typographical Conventions Example Desorption while Courier font bold indicates a program a fragment of a program or a Dynamic
16. Periodic Timer Interrupts 0 2 2 2 Calling Sequence sss The Driver essere The Fastcall Driver sess Virtual Watchdog Timers Global Initialization 2 Chapter 5 Real Time Kernels The Simplified Real Time Kernel The Real Time Kernel sss Kernel Restrictions on Use of Suspend Internals Chapter 6 Failure and Recovery Software Failures eese Hardware Hardware Watchdog Timer Reset and Super Reset sss Recovery of Protected Variables Chapter 7 The Five Key System Operator 2 00 440 9 0 Programmer Features 2 2 2 Special Key Five Key 2 Reading the Keypad without FK LIB Chapter 8 RS 232 Communication Serial Communication sse Send and Receive Buffers Echo Option 4c oen CTS RTS Control eene XMODEM File Transfer Modem Communication iv Table of Contents Dynamic C 32 v 6 x Function Libraries and Sample Programs 66
17. 32 v 6 x 6 FAILURE AND RECOVERY Recovery from failures 1 a complex subject that is beyond the scope of this manual Chapter 6 discusses the following topics briefly Software failures Hardware failures The watchdog timer Reset and super reset Protected variables Application Frameworks Failure and Recovery 51 Even if a program is written and compiled correctly the program may still crash because of conditions that are beyond the control of the programmer and the compiler For example blackouts brownouts and power spikes can put the controller in an unpredictable state Therefore crash detection and recovery is an important issue for all embedded applications Z World is aware of this issue and has derived methods and support routines to facilitate the development of robust embedded systems As a rule the logic associated with the detection and handling of errors can be expected to be a substantial portion of a program s overall code Z World provides various ways to detect failures Software Failures Certain software related failures can be actively verified For example if the program is compiled with the debugging options activated the compiler inserts code to do the following 1 Check for stack integrity 2 Check for pointer store validity 3 Check for array bound overflowing If such exceptions occur the debugging code generated by compiler calls the routine exception which in t
18. A master message is composed as shown here slave id len 1 hi CRC 10 The slave s response is composed as shown here len 1 1 CRC hi CRC lo The term len is the length of the message that follows During a transfer from the master the address byte is transferred in the ninth bit of the address mode and only the slave that matches this address will listen to the rest of the message which 1 sent in regular 8 bit data mode Hardware Connection Figure 9 1 shows the connections for a two wire RS 485 network Any Z World s controller can be a master or a slave There should only be one master but there can be up to 255 slaves 1200 485 Rx O PK2100 11600 485 BL1100 485 PK2200 485 1 485 s and others BL1400 485 Tx 0 4 and others oo Figure 9 1 Two Wire RS 485 Network Connections with Z180 Port 1 76 Master Slave Networking Dynamic C 32 v 6 x Some Z World controllers such as the 2200 half duplex RS 485 ports Other controllers such as the PK2100 have full duplex RS 485 ports A full duplex RS 485 port can be made into a half duplex RS 485 port by connecting RX to and RX to TX Software Support void op init 21 char baud char rbuf byte address Initializes 7180 Port 1 for RS 485 ninth bit protocol binary communi cation The data format defaults to 8 bits no parity 1 stop bit baud selects
19. C keyword or phrase 01 Program comments are written in Courier font plain face Italics Indicates that something should be typed instead of the italicized words e g in place of filename type a file s name Sans serif font bold signifies a menu or menu selection An ellipsis indicates that 1 irrelevant program text is omitted for brevity or that 2 preceding program text may be repeated indefinitely Brackets in a C function s definition or program segment indicate that the enclosed directive is optional Angle brackets occasionally enclose classes of terms A vertical bar indicates that a choice should be made from among the items listed Application Frameworks About This Manual ix X About This Manual Dynamic C 32 v 6 x CHAPTER 1 INTRODUCTION Application Frameworks Introduction 11 Dynamic C combines C compiler an editor and source level debugger The Dynamic C development system runs on IBM or compatible PCs The target controller connects to a serial port on the PC and typically communicates at 19 200 to 57 600 baud Dynamic C allows the user to develop software on the target controller interactively Dynamic C includes many useful features such as the following Direct compilation to the target controller s memory Compila tion linking and downloading occur simultaneously Compilation to File EPROM files or downloadable files that work with the Z World Download
20. Declare variables accessible in interrupt service routines as shared to prevent errors There is no operating system to handle interrupts in a real time program that runs stand alone on a controller Furthermore real time applications require far more than a generic response to interrupts Dynamic C makes writing interrupt routines just as easy as writing any C functions but this does not mean that real time software 1s easy to de velop A major issue for the real time programmer is interrupt latency Interrupt Latency Interrupt latency 1s usually defined as the worst case delay between an interrupt request and the start of the interrupt service Typical values for this delay are about 100 microseconds Low interrupt latency is necessary when speed is important or when it is important that an interrupt not be missed such as a periodic timer inter rupt Causes A delay between an interrupt request and the start of the interrupt service can occur for several reasons 1 The current instruction must finish executing This is never more than 14 clock periods on the Z180 2 The return address must be pushed on the stack This is about 10 more clock periods 3 Atomic store and read operations associated with shared and protected variables result in interrupts being disabled for about 10 microseconds a 9 MHz processor Atomic structure assign ments of course can cause longer delays The above mentioned delays are rela
21. Manager are easy to create with Dynamic C Embedded assembly language It is possible to write entire functions in assembly language or include portions of assembly language in a C program Assembly language is sometimes important for performance in time critical programs Z World has made innovative extensions to the C language The costatement makes cooperative multitasking very convenient The shared keyword makes access to a variable atomic so that the integrity of the variable can be maintained among different tasks The protected keyword causes the compiler to keep a backup copy of the variable during modification so that it can be reconstructed after a catastrophe such as a power failure Inter rupt service routines can be written in These and other extensions to C simplify the task of building robust systems Z World software libraries support real time programming networking and serial communication 12 Introduction Dynamic C 32 v 6 x 2 REAL TIME PROGRAMMING Programmers should be aware of certain issues regarding real time programming Real time systems thrive on interrupts and interrupt processing Chapter 2 discusses the following topics Interrupt Latency Multitasking Application Frameworks Real Time Programming 13 Interrupts can occur at any time in particular the middle of a write to multibyte variables anything except char The variable value can be indeterminate
22. are always enabled String messages can be set up with the following call 5key setmsg message no the message The message no can be from 0 to 9 The message corresponding to the message no can be changed at any time Passing NULL instead of a message will turn off that particular message Application Frameworks Old 5 Key System 91 Linked list parameters can also be displayed They are set through the _5key_setmenu calls The previously mentioned boiler temperature Tb can be displayed periodically with this call 5key setmenu Menul Tb 5 Fdata amp Tb 300 00 100 00 Tb help sizeof Tb help MODIFY 10 DISPLAY If the menu setup 1 code driven it 1s still possible to use the linked list but 5key menu cannot be called Software Alarms Four variables ALARM1 ALARM2 ALARMS and ALARMA are moni tored by the five key system When any of these software alarms becomes nonzero the five key system resets it to zero and calls a specified func tion It handles the functions keys the same way and except for alarms the triggers are generated in software The alarm service 1 particularly useful when an alarm condition has to transfer control of the display and keypad to a predefined function Alarm handlers might be loaded as follows 5key setalarm alarml alarm2 alarm3 NO FUNCTION Here function alarm1 is executed whenever Alarm 1 signals Alarms 2 and 3 each have handlers However
23. character Otherwise the software has to check for both terminating characters The message terminating character cannot be any of the ASCII characters used in the modem commands nor can it be a line feed character 0x0A The software supports communication with a Hayes Smart Modem or other compatible modem The CTS RTS and lines of the modem not used If the modem used is not truly Hayes Smart Modem compatible tie the CTS RTS and DTR lines on the modem side together The CTS and RTS lines on the controller side also have to be tied together Application Frameworks RS 232 Communication 65 NULL connection is also required for the TX and RD lines since both the controller s serial port and the modem are data communication equipment DCE A commercial NULL modem would have its CTS and RTS lines tied together on both sides Figure 8 1 shows the correct modem to controller serial connections The ISA COM ports 1 and 2 can be connected directly to a modem since they are already data terminal equipment DTE Modem Controller Side Side RX RX TX TX GND GND RTS RTS CTS 5 CTS DTR Figure 8 1 Modem to Controller Serial Connections Function Libraries and Sample Programs Software Support The functions in this section are described for Port 0 of the Z180 Similar functions exist for the Z180 Port 1 SIO Ports 0 and 1 SCC Ports A and B the XP8700 expansion card and ISA COM Ports 1 and 2 uu See
24. error longjmp savreg 1 Detecting Errors In waitfor Statements Sometimes there may be a time limit on how long to wait for a certain condition costate xxx always waitfor DelayMs 200L x if x x not set and we can t wait errorflag 1 any longer abort It is important that x not change between the test in the waitfor and the test following the waitfor There would be no risk of change if x reflects a condition that is updated for example at the top of a costatement loop and remains stable through out the loop If x is subject to change then a different scheme such as the following could be used costate xxx always on waitfor flag DelayMs 200L x if flag x not set and we can t wait errorflag 1 any longer abort waitfor and Problems with Evaluating C Expressions A potential problem arises with the logical operators OR and amp amp AND which are subject to short circuit evaluation rules Remaining terms in OR expression suchasa b not evaluated if any of the preceding terms are true Remaining terms in an AND expres sion such 66 b amp amp c not evaluated if any of the preceding terms are false Application Frameworks Costatements 35 Furthermore the DelayMs routine does not start its time delay until it is actually called An expression such as waitfor test amp amp DelayMs 50L has th
25. incremented by system every sec if state 1 if buttonpushed state 2 turnondevicel timerl time 1 if state 2 if time timerl gt 60L state 3 turnondevice2 timer2 time 1 if state 3 if time timer2 gt 601 state 1 turnoffdevicel turnoffdevice2 other tasks or state machines Solving the Problem With Costatements The Dynamic C costatement provides an easier way to implement the task costate task 1 costate task 2 waitfor buttonpushed turnondevicel waitfor DelaySec 60L turnondevice2 waitfor DelaySec 60L turnoffdevicel turnoffdevice2 costate task n Application Frameworks Costatements 23 This solution is elegant simple Note that the costatement the one that is written out looks much like the original description of the problem the branching nesting and variables within the task are hidden in the implementation of the costatement and its waitfor statements Summary The Dynamic C costatement provides a formalized way of generating code that advances until it encounters a point in the logic where it is necessary to create a delay or wait for an event Waiting is accomplished by jumping out of the costatement to allow the larger loop to continue execution Whenever a costatement is defined the compiler creates an associated CoData data structure at the sa
26. is also disabled 78 Master Slave Networking Dynamic C 32 v 6 x void zl op int This is an interrupt service routine for the Z180 Port 1 used in master slave networking Sample Program MASTER C running in slave controller The master sends a string of messages to the slave Slave replies The master prints the reply at STDIO char rbuf 255 receive buffer char reply 40 xeply buffer char msg 40 message buffer main int i j ercode VdInit initialize 19200 baud receive and master op init z1 16 rbuf 0 j 1 while 1 wait 10000 counts before polling for i 0 i 10000 1 runwatch sprintf msg Message d j send message to slave 1 and wait for reply ercode TalkToSlave 1 msg strlen msg 3 reply if ercode 1 if reply is valid printf s n reply 1 if bad reply or link failure printf Link Failure or Bad Link n int TalkToSlave int slave no char query int len int ndelay char reply int i ercode sends message and waits for reply ercode sendOp22 slave no query len ndelay if reply is valid copy to reply buffer if ercode 1 for i 0 i lt rbuf 0 2 1 reply i rbuf 1 i reply i N0 return ercode continued Application Frameworks Master Slave Networking 79 SLAVE C running in slave controller The slave waits for a message fr
27. message terminated with CR while Dread z0 buf CR 0 here you could do whatever you want with the message in this example the message is sent back DzOsend prompt Dwrite z0 buf strlen buf send message back then some more DzOsend prompt Dwrite zO it works 9 write another DzOsend prompt Application Frameworks RS 232 Communication 69 modem communication set ismodem to 1 baud rate is either 2400 or 1200 The above example above will work just as well when the PC has dialed up the controller connected to a modem Z World recom mends using a Hayes compatible Smart Modem Otherwise the modem connected to the controller would have to have its RTS 4 CTS 5 and DTR 20 lines tied together Also NULL modem is required for the serial connection between the modem and the controller s serial port The equivalent program for the serial communication controller SCC Port A would be as follows char buf 20 messages Dinit sca rbuf tbuf 200 384 mode baud ismodem isecho Dscasend prompt send a prompt while 1 wait for a message terminated with CR while Dread sca buf CR 0 here you could do whatever you want with the message in this example the message is sent back Dscasend prompt Dwrite sca buf strlen buf send message back then some more Dscasend prompt Dwrite sca it works 9 write another Dscasen
28. or modules In this case each task 15 specified to run every ticks by calling every function once as part of the program initialization 44 Real Time Kernels Dynamic C 32 v 6 x For example the following scheme could be used for a task to turn on a valve each time the liquid level in a tank is low main run_every 4 100 task4 every 100 ticks task4 if level lt LOW openvalve if level gt HIGH closevalve return If ticks occur 50 times per second then the state of the valve will be sampled every two seconds A very small amount of execution time will be expended on this task If the nature of the task is such that there are several sequences of code separated by dead time awaiting an external event or waiting for a fixed time to elapse then the suspend function could be invoked In the above example suppose that in order to open the valve a motor must start run for approximately three seconds until a contact is closed indicating that the valve is fully open and then the motor must be turned off Assume that the task of closing the valve is similar and that ticks occur 50 times per second The following code could be used task4 if level lt LOW amp amp valveclosed motor OPEN while valveclosed suspend 5 motor OFF 1 if level gt HIGH amp amp valveclosed motor CLOSE while valveclosed suspend 5
29. or time delays are not required a cooperative multitasking environment does not require a timer interrupt The following advantages are offered by cooperative multitasking Much easier communication between tasks Greater predictability of mutual task interaction Much simplified programming Dynamic C has a language extension called the costatement to support cooperative multitasking In essence a costatement 15 a cooperative task Refer to Chapter 3 Costatements and to the Dynamic C 65 Technical Reference manual for more information Preemptive Multitasking Preemption means tasks are interrupted and control is taken away involun tarily by an interrupt We say a task 1 preempted by another task perhaps of a higher priority task has no control of when preemption may take place when preemption is enabled but a task can turn off preemption altogether by disabling interrupts 16 Real Time Programming Dynamic C 32 v 6 x preemptive multitasking environment needs a kernel to stop and start tasks This software that monitors regulates and dispatches tasks usually uses a timer interrupt to indicate when it is time to preempt the currently active task Because a task does not know when preemption may take place program mers must be careful when variables are shared among preemptive tasks Cooperation and thus communication among preemptive tasks is the major problem The real time kernel RTK supplied wi
30. ports reg 66 COMMAND mode 65 command protocol master slave 76 communication 232 64 67 68 69 RS 485 76 77 78 81 serial 64 67 76 71 78 81 master slave 77 78 COMPAS 46 compile time interrupt directive 72 connections RS 485 two wire network 76 CONTENE epe cedet ER 27 28 controller execution speed arithmetic 22222 44 84 logical decision making 84 cooperative multitasking 16 17 COPAUSE une eee 30 CoReset 26 27 30 33 34 CORCSUME 30 costate 25 30 32 33 35 Index 95 costatements 16 21 22 23 26 42 3 0 ento 30 always 25 delay functions 29 dependencies 32 ETTOL EXIT 1nd 33 firsttime flag and functions 28 granularity 31 Init CODE secto 25 natned 2o onu 25 Nested 33 problems with C expression evaluation 35 eec e TREES 25 timing considerations 3 unnamed eee 25 waitfor 29 31 35 36 yield he 29 CRC cyclic redundancy check 76 77 78 computing 73 73 CS State tede 26 27 CIS re teet 67 68 CTS R ES 65 cyclic redundancy check 76 77
31. the ISA COM Port 1 COM2REM C RS 232 communication with the ISA COM Port 2 74 RS 232 Communication Dynamic C 32 v 6 CHAPTER 9 MASTER SLAVE NETWORKING Z World supports master slave networks using 2 wire and 4 wire RS 485 networks The master and slave controllers communicate using a protocol based on the ninth bit Chapter 9 discusses these topics Communication protocol Hardware connections Software support Libraries and sample programs Application Frameworks Master Slave Networking 75 Z world has library functions for master slave two wire half duplex RS 485 9 bit binary communication This protocol 15 supported only on Z180 Port 1 which is configured for RS 485 communication on most Z World controllers Boards that provide access to Z180 Port 1 can be the master or the slave There should only be one master which will then have a board address of 0 The slaves must have their own distinct identification numbers from 1 255 The functional support for the master slave serial communication consists of the following steps 1 Initialization of Z180 Port 1 for RS 485 communication 2 Master sends inquiry and waits for response from a slave 3 Slaves monitor for their address during the ninth bit of a transmission The targeted slave replies to the master Communication Protocol The binary command message protocol adopted 1s similar to that used for the Opto 22 binary protocol
32. the syntax type name value e g int 0 as a constant that cannot be changed when compiled to ROM The GLOBAL INIT segment provides a way to perform this type of initializa tion int i GLOBAL INIT i 0 The function chain GLOBAL INIT also initializes CoData structures for costatements and must be called before a program can use costatements 40 The Virtual Driver Dynamic C 32 v 6 x 5 REAL TIME KERNELS Two function libraries support preemptive multitasking These are the real time kernel RTK LIB and the simplified real time kernel SRTK LIB Chapter 5 discusses these topics The simplified real time kernel Thereal time kernel e Kernel functions Application Frameworks Real Time Kernels 41 The real time kernel and the simplified real time kernel SRTK included with Dynamic C s function libraries The RTK and SRTK allow a program to be divided into tasks by priority These tasks can be treated as separate programs running independently of one another The execution of the tasks is interleaved in time There are two main advantages to this 1 More urgent tasks higher priority are performed in preference to less urgent tasks 2 Itis easier to write and organize a program when separate tasks or sequences of events can be handled as if they were isolated from one another The RTK allows many levels of priorities but the SRTK has only the three levels listed in Tabl
33. 100 beeper loop while SRTK works while 1 background processing HIGH PRIORITY TASK srtk hightask fk monitorkeypad continued next page Application Frameworks The Five Key System 57 LOW PRIORITY 5 srtk lowtask fivekey lo task 5 int fivekey lo task costate fk helpmsg put up help messages PutMenus user keys process user keys int PutMenus extern char fk newmenu int choice costate loop through all the menus lcd erase led printf 01 time date menu fk newmenu 0 for begin menu 1 waitfor fk item setdate Time if fk newmenu break waitfor fk item settime Time if fk newmenu break end menu 1 lcd erase printf 0x000000001 I O Menul fk newmenu 0 for begin menu 2 waitfor item enum enum sel 85 amp choice first second third last 0 if fk newmenu break waitfor fk item int integer 4d amp 1 10 1000 if fk newmenu break waitfor fk item unsigned int unsigned int 2u amp u 0 10 if fk newmenu break waitfor fk item alpha Alpha strng strlen strng if fk newmenu break waitfor fk item float Float 8 4f amp 900 9999 if fk newmenu break end menu 2 end menu loop end costatement return 1 int user keys n handle bottom row k
34. 16 17 18 ELE 49 problems with C expression evaluation 35 Program Loader Utility PLU senate 72 programmable reload timer PRT 43 73 programming 56 protected variables 14 15 crash 54 protocol command master slave 76 R RAM battery backed 53 54 rbuf 78 read only memory 72 real time kernel 17 38 39 42 43 48 70 72 78 88 and the old Five Key system 88 and virtual driver 43 array of RTK task pointers 43 sample programs 49 real time programming 13 Application Frameworks receive buffer 64 68 69 77 78 Initialization 67 reading sott 68 reload 22 72 replyOpto22 78 Tequest 45 46 88 89 53 7180 73 restarting modem communication 72 restrictions on use of suspend 47 rkernel sss 48 ROM programmable 72 RS 232 communication 64 67 68 69 features uet 64 circular buffers 64 CTS RTS Control 65 modem communication 65 XMODEM file transfer 65 interrupt handling 67 serial 1
35. 53 and real time kernel 39 fastcall su ee 39 global initialization 40 virtual watchdog 38 40 53 Dynamic C 32 v 6 x waitfor 25 27 28 29 31 32 33 35 36 39 watchdog timer 40 52 X Rata erro 71 XMODEM commands 70 protocol 64 65 70 XP8700 ten 66 72 Application Frameworks Y yield 24 25 27 29 Z LO inset RO ERE US 72 720 68 720 68 Zl 79 80 OEE E 64 66 Port 0 67 68 69 72 78 79 Initialization 77 Serial Channels 0 1 disabling interrupts 73 Index 101 102 Index Dynamic 32 v 6 Z WORLD Z World Inc 2900 Spafford Street Davis California 95616 6800 USA Telephone Facsimile Web Site E Mail 530 757 3737 530 753 5141 http www zworld com zworld zworld com Printed in U S A
36. 6 x The csstate field applies only if the costatement has a name CSState flag has no meaning for unnamed costatements Last Location The two fields lastlocADDR and lastlocCBR represent the 24 bit address of the location at which to resume execution of the costatement If lastlocADDR is zero as it is when initialized the costatement executes from the beginning subject to the CSState flag If 1astlocADDR is nonzero the costatement resumes at the 24 bit address represented by lastlocADDR and lastlocCBR These fields are zeroed when 1 the CoData structure is initialized by a callto GLOBAL INIT CoBegin or CoReset 2 the costatement 1s executed to completion or 3 the costatement is aborted Check Sum The ChkSum field is a one byte check sum of the address It is the exclusive or result of the bytes in lastlocADDR and lastlocCBR If ChkSum is not consistent with the address the program will generate a run time error and reset The check sum is maintained automatically It 1 initialized by GLOBAL INIT CoBegin and CoReset First Time The firsttime field is a flag that is used by waitfor statements It is set to 1 before the waitfor expression is evaluated the first time This aids in calculating elapsed time for the functions DelayMS DelaySec and DelayTicks Content The content field a union is used by the costatement delay routines to store a delay count Check Sum 2 The ChkSum2 field is currently unused
37. 7 5 425 Table A 2 lists the execution times of various logical and counting operations for a 9 216 MHz clock Table A 2 Execution Times of Logical Operations Operation Execution Time if k 2 6 us for k 0 k lt 100 k 12 8 us for loop overhead sub 5 8 us subroutine call overhead with 1 integer argument switch n first case 22 us each additional case 7 us costate 32 us costatement entry exit overhead costate waitfor 0 19 costatement waiting 84 Execution Speed Dynamic C 32 v 6 x Table 3 lists the execution times of other operations These times are approximate times assuming a typical environment Hand coding in assembly language or other special care can result in substantially in creased performance Table A 3 Execution Times of Other Operations Operation Execution Time Response to an interrupt or interrupt latency 100 us Sustained data throughput interrupt driven 20K bytes per second Burst data using DMA 500K bytes per second Application Frameworks Execution Speed 85 86 Execution Speed Dynamic C 32 v 6 x B OLD 5 SYSTEM Application Frameworks Old 5 Key System 87 The old five key system 15 a set of functions 5 LIB and 5KEYEXTD LIB that has the all of the functionality of the newer FK LIB and a few additional features But the old five key system
38. LM 32 for Zilog 7180 microprocessors Version 6 x Integrated C Development System Application Frameworks 019 0081 020330 Dynamic 32 v 6 x Application Frameworks Part Number 019 0081 020330 B Printed in U S A Copyright O 2002 Z World Inc All rights reserved Z World Inc reserves the right to make changes and improvements to its products without providing notice Trademarks Dynamic C is a registered trademark of Z World Inc PLCBus is a trademark of Z World Inc Windows is a registered trademark of Microsoft Corporation Hayes Smart Modem is a registered trademark of Hayes Microcom puter Products Inc Notice to Users When a system failure may cause serious consequences protecting life and property against such consequences with a backup system or safety device is essential The buyer agrees that protection against consequences resulting from system failure is the buyer s responsibility This device is not approved for life support or medical systems Company Address Z World Inc 2900 Spafford Street Z Y VOKLD Davis California 95616 6800 USA Telephone 530 757 3737 Facsimile 530 753 5141 Web Site http www zworld com E Mail zworld zworld com TABLE CONTENTS About This Manual vii Chapter 1 Introduction 11 Chapter 2 Real Time Programming 13 Interrupt Latene yos sie e ein etre nere 14 CAUSES coe Rom Ob eats 14 Neste
39. M port on the PC usually 2 which by default operates at 19 200 bps Features which were formerly only available in the Deluxe version are now standard Dynamic C 32 supports programs with up to 512K in ROM code and constants and 512K in RAM variable data with full access to extended memory The Three Manuals Dynamic C 32 is documented with three reference manuals Dynamic C 32 Application Frameworks Dynamic C 32 Technical Reference Dynamic C 32 Function Reference This manual discusses various topics in depth These include the use of the Z World real time kernel costatements function chaining and serial communication The Technical Reference manual describes how to use the Dynamic C development system to write software for a Z World programmable controller The Function Reference manual contains descriptions of all the function libraries on the Dynamic C disk and all the functions in those libraries DU Please read release notes and updates for late breaking information about Z World products and Dynamic C Application Frameworks About This Manual vii Assumptions Assumptions are made regarding the user s knowledge and experience in the following areas e Understanding of the basics of operating a software program and editing files under Windows on a PC Knowledge of the basics of C programming Dynamic C is not the same as standard C For a full treatment of C refer to the following texts
40. Task If all goes well the first costatement will be executed at the periodic rate The second costatement will however be delayed by the first costatement The third will be delayed by the second and so on The frequency of the routine and the time it takes to execute comprise its granularity If the routine executes every 25 milliseconds and the entire group of costatements executes in 5 to 10 milliseconds then the granularity is 30 to 35 milliseconds Thus the delay between the occurrence of a waitfor event and the statement following the waitfor can be as much as the granularity 30 to 35 milliseconds The routine may also be interrupted by higher priority tasks or interrupt routines increasing the variation in delay The consequences of such variations in the time between steps depends on the program s objective Suppose that the typical delay between an event and the controller s response to the event is 25 milliseconds but under unusual circumstances the delay may reach 50 milliseconds An occa sional slow response may have no consequences whatsoever If a delay is added between the steps of a process where the time scale is measured in seconds then the result may be a very slight reduction in throughput Consider the delay between sensing a defective product on a moving belt and activating the reject solenoid that pushes the object into the reject bin If such a critical delay cannot exceed 40 milliseconds then a system will som
41. The Implementation of Costatements yield At a yield statement the processor 1 stores the address of the following statement in lastlocADDR and lastlocCBR as the resume address and 2 exits the costatement Consequently when the costatement is executed again it continues from the statement that follows the yield statement abort At an abort statement the processor 1 resets lastlocADDR and lastlocCBR to zeros to indicate the costatement is reset and 2 exits the costatement block Application Frameworks Costatements 27 waitfor The waitfor statement can be viewed as the following equivalent code x gt firsttime 1 while yield where x gt firsttime will become 0 reset by Dynamic C after the expression is evaluated In this code x is the CoData structure corre sponding to the costatement The field firsttime indicates whether it is the first time the expression is evaluated The firsttime Flag and firsttime Functions firsttime function is a delay function that can be called from a waitfor statement For example the first time the DelayMs function is called it must set up the countdown variables for the specified amount of delay stored in the field content of a CoData structure All subsequent calls to DelayMs merely check whether the delay has expired The initialization flag must be associated with the CoData structure because several costatements may call DelayMs A firsttime functio
42. ample checks for the event every 20 ticks until the event takes place at which point execution continues The suspension can be up to 65 535 ticks Restrictions on the Use of Suspend When a task 1 suspended the saves the top of the stack as much as Is associated with the task in a special static array This array has a default size of 50 bytes per task This array larger can be made larger if the task has many auto variables by changing TASKSTORE SIZE which is defined in the library When a suspended task resumes execution the top of the stack 1 restored to its previous state However the value of the stack pointer can differ because lower priority tasks may have started or stopped during the suspend They may have had their state saved on or restored from the stack These problems can result from the actual absolute address of the stack frame changing Pointers to auto variables or arguments within the task or its subrou tines can point to the wrong location after a suspend Avoid this problem by using auto variables or arguments only in routines that do not suspend directly or indirectly through a subroutine Be very careful about pointers to auto variables or use only static variables The code generated by the compiler uses the IX register as a stack frame pointer under the useix option This creates problems when using suspend After a suspend the IX pointer is adjusted for any change in the stack s absolu
43. at they need only to save the registers that they use while the C interrupt routine assumes that every thing possible must be saved Assembly language also has more direct access to the machine registers Nested Interrupts With sufficient care it 1 possible to reenable interrupts inside an interrupt routine This lessens the interrupt latency because interrupts do not stay disabled for the duration of the interrupt handler In general the cause of a type X interrupt should be removed before interrupts are reenabled for the type X interrupt When this 15 done one interrupt routine can interrupt another interrupt routine For example a serial port interrupt routine on the Z180 can reenable interrupts in general while disabling the serial port interrupt specifically The serial port interrupt can then be reenabled upon returning from the interrupt routine However such a practice can create difficulties particularly if a nested interrupt lasts for a long time There is no way to get back to the original interrupt service until the nested interrupt is complete at which point some data may be lost A logical solution in this situation 1s to establish a software flag that prevents a lengthy task from interrupting a service routine Were this idea taken to extremes there would eventually be an operating system where every interrupt is logged by the operating system and then dispatched in a priority order Z World provides two real time kernel
44. bytes When a value is stored in this variable it typically takes two or more instructions to perform the store to memory If an interrupt occurs between these store instructions and a new task of higher priority that uses the same variable takes over then the new task will see a corrupted value partly old and partly new Such nonatomic writes can be made atomic by disabling the interrupts to prevent this situation DI fnum xnum 5 34 EI DI disables the interrupts assuring that no other task will begin executing until the computation is complete EI then enables the interrupts The keyword shared declares a variable to be atomic Dynamic C automatically handles interrupts on stores and fetches of shared variables Shared float 1 f2 atomic variables Interrupts if enabled will be disabled before a multi instruction load or store Following the load or store interrupts are then restored to their previous state Byte fetches and stores are naturally atomic and nothing needs to be done Loads and stores of 16 bit data may or may not need their interrupts disabled depending on the type of processor instruction used 18 Real Time Programming Dynamic C 32 v 6 x If a structure is declared shared then any fetch of an element will be atomic An assignment that causes the entire shared structure to be moved in memory is also atomic Application Frameworks Real Time Programming 19 20 Real Time Programming Dyna
45. char CSState unsigned int lastlocADDR char lastlocCBR char ChkSum char firsttime union unsigned long ul struct unsigned int ul unsigned int u2 us content char ChkSum2 CoData CSState The csState field contains two flags STOPPED and INIT The functions CoBegin CoReset CoPause and CoResume set these two flags The functions isCoDone and isCoRunning report these flags Table 3 1 summarizes the meanings of the STOPPED and INIT flags Table 3 1 Explanation of STOPPED and INIT Flags in CSState STOPPED Meaning Yes Yes The costatement either is done or has been initialized to run from the beginning but set to inactive This condition can be set by CoReset Yes No The costatement is paused waiting to resume execution from wherever it was paused This condition can be set by CoPause Yes The costatement has been initialized to run from the beginning and will run when the program execution reaches it This condition can be set by CoBegin No The costatement is active and running and will resume execution where it left off when the program execution reaches it This is the normal condition of a running costatement CoResume will return the flags to this state The function isCoDone returns true 1 if both the STOPPED and INIT flags are s et The function isCoRunning returns true 1 if the STOPPED flag is not set 26 Costatements Dynamic C 32 v
46. ction prot recover will check the flag and reestablish the correct version The following code shows how the previous example would be modified to include recovery for protected variables protected long CriticalVar CCVer is the version of the compiler Sec is the number of seconds from the beginning of 1980 main int CCVer unsigned long Sec static unsigned long CurSec if Sec CurSec super reset prot init CurSec Sec perform super initialization 1 reset due to crash prot recover perform recovery The function prot init initializes Dynamic C s internal protection data structure Call prot init before setting CurSec The function prot recover recovers the damaged variable Note that only one variable could possibly be damaged 1 system failure occurred 54 Failure and Recovery Dynamic C 32 v 6 x 7 THE SYSTEM The five key system is a library of functions FK LIB supporting human use of the LCD and the keypad on Z World s PK2100 and PK2200 series controllers Chapter 7 discusses the following topics Features for the operator Features for the programmer The five key functions Application Frameworks The Five Key System 55 The five key system uses the LCD and the keypad Z World s 2100 and PK2200 series controllers Figure 7 1 shows the standard assignment of the keys on the keypad item field
47. d Interrupts ce ect ter 15 Multitasking snan anna a 16 Cooperative Multitasking 2 16 Preemptive Multitasking 16 Tips for Multitask Programming 18 Assign Priority Levels essere 18 Identify Shared Variables see 18 Chapter 3 Costatements 21 Solving Problems with Costatements 22 Solving Problems Without Costatements eese 23 Solving the Problem With Costatements ees 23 T 24 Costatement Functions 25 P 25 State ca d Sem gu hima 25 The CoData Struct te 2 n eftt 25 The Implementation of Costatements 8 27 The firsttime Flag and firsttime Functions 22 28 Associated Keywords and Functions sse 29 Delay Functions HUI e eR 29 Other Functions e i a e ar ROI eem 30 Costatement Topics E A gestus 30 Timing I88068 5 0 ori eS RH INR 30 Dependency Relations Among Costatements 32 Nesting Costatements sess 33 Error Exits from Costatements sse 33 Detecting Errors In waitfor Statements sss 35 waitfor and Problems with Evaluating C Expressions 35 Application Frameworks Table of Contents iii Chapter 4 The Virtual Driver
48. d prompt serial communication software implements delays with the suspend function of the real time kernel RTK when the RTK is used Otherwise the delays are implemented with a software countdown loop XMODEM Commands e int Dxmodem z0down char buffer int count Sends downloads count 128 byte blocks in buffer using the XMODEM protocol The function returns 0 timed out no transfer successful transfer 2 canceled transfer canceled by receiver e int Dxmodem zOup unsigned long address int pages int dest int parser Receives uploads a file using XMODEM protocol The parameters are described below 70 RS 232 Communication Dynamic C 32 v 6 x address the physical address in RAM where the received data is pages dest to be stored If the receive buffer is allocated by xdata then the name of the array may be used for the address argument If however the data area 1 allocated using normal C the logical address of the buffer must first be converted to a physical address using the library function phy adr the number of 4 kbyte blocks of data that have been transferred If an RS 485 master slave network is set up specify dest 0 when the upload is intended for the master If dest 15 nonzero the upload is intended for the designated slave parser the function that handles parsing of the uploaded data The function returns 0 timed out no transfer 1 successf
49. e waitfor function args function outline int function args costate flag 0 body of costatement flag 1 return flag In this case the subroutine is called repeatedly each time the execution thread passes through the waitfor The subroutine returns zero each time until the execution of the costatement is completed when it returns a one satisfying the waitfor in the upper level costatement This approach has the additional advantage of providing local variables and arguments that are passed A disadvantage is that the arguments must be passed repeatedly Error Exits from Costatements In special circumstances such as the failure of a communication link it may be necessary to make an error exit from a costatement or group of costatements A costatement can be aborted either statically by writing abort in the costatement directly or dynamically by calling the function CoReset to terminate a remotely executing costatement costate xxx always on if bad condition abort OR if bad condition CoReset amp xxx Application Frameworks Costatements 33 Use of setjmp 1ongjmp for Error Exit Programmers use the setjmp and long jmp functions to perform an error exit from nested functions If the nested functions contain costatements it is usually necessary to reinitialize the costatements as a part of the error exit When costatements are nested the nesting 15 usually reb
50. e perhaps unexpected result of waiting until test 1 true and then waiting 50 milliseconds more Because of short circuit evaluation rules DelayMs will not be evaluated if test is false If the order of the terms is reversed waitfor DelayMs 50L amp amp test it waits for test but not less than 50 milliseconds It is possible to avoid short circuit evaluation problems by using the bitwise AND and OR operators and amp 36 Costatements Dynamic C 32 v 6 x CHAPTER 4 THE VIRTUAL DRIVER The virtual driver is a set of functions available for Z World controllers that provides several services Chapter 4 discusses the following topics Periodic timer interrupts Global initialization Application Frameworks The Virtual Driver 37 Periodic Timer Interrupts To invoke the virtual driver a program must include VDRIVER LIB in its list of libraries A call to VdInit must be included at the beginning of the program The virtual driver 15 called 1280 times per second by a clock interrupt If no real time kernel fastcall or virtual watchdog is in use the virtual driver just updates the second millisecond and tick timers used by the DelaySec DelayMs and DelayTicks functions Figure 4 1 summarizes the operation of the virtual driver at each clock interrupt discussed in this chapter Enter virtual driver on timer interrupt every 1 1280 second Increment tick counter Service millisecond timer
51. e 5 1 Table 5 1 Simplified Real Time Kernel Priorities Name Frequency Priorit srtk_hightask Every 25 ms am srtk lowtask Every I 100 ms E none Background lowest lowest The background task is code that executes when no other task is executing The virtual driver s FASTCALL service can be used with either kernel to implement a very high priority task Each RTK or SRTK task can contain multiple execution threads by using costatements The Simplified Real Time Kernel Unlike the RTK the SRTK requires no function pointers to tasks The routines srtk hightask and srtk lowtask are called every 25 milli seconds and every 100 milliseconds respectively by the virtual driver 1f 1 SRTK LIB is used 2 RUNKERNEL is defined 3 the virtual driver is initialized and 4 init srtkernel has been called The following example shows a complete simple program using the SRTK duse vdriver lib or include VDRIVER LIB and duse srtk lib SRTK LIB in LIB DIR define RUNKERNEL 1 use the kernel int HCOUNT LCOUNT 42 Real Time Kernels Dynamic C 32 v 6 x HCOUNT LCOUNT 0 VdInit Need virtual driver init _srtkernel Initialize the SRTK while 1 stay alive while SRTK works This high priority task executes every 25 ms srtk_hightask HCOUNT This low priority task executes every 100 ms srtk_lowtask LCOUNT costate print e
52. e it exits The costatement will then termi nate If the costatement is always on the next time the program reaches it it will restart from the top If the costatement is not always on it becomes inactive and will not execute again until turned on by some other software Unnamed costatements are always on Other Functions void CoBegin CoData cd CoBegin initializes a CoData structure The INIT flag is set but the STOPPED flag is clear void CoReset CoData cd CoReset resets a CoData structure The STOPPED and INIT flags are both set void CoPause CoData cd CoPause pauses CoData structure The STOPPED flag 1 set but the INIT flag is clear void CoResume CoData cd CoResume resumes CoData structure The STOPPED and INIT flags are both clear int isCoDone CoData cd The function isCoDone returns true 1 if both the STOPPED and INIT flags are set Otherwise it returns 0 int isCoRunning CoData cd The function isCoRunning returns true 1 if the STOPPED flag is not set Otherwise it returns 0 Costatement Topics Timing Issues Costatements in most instances are grouped as periodically executed tasks A costatement can be part of a real time task which executes every n milliseconds as shown in Figure 3 2 30 Costatements Dynamic C 32 v 6 x enter every n milliseconds costate costate costate costate Figure 3 2 Costatement as Part of Real Time
53. eply in the following format len 1 1 CRC hi CRC lo reply the slave s reply string count the length of the reply The longest reply is 252 bytes because two CRC bytes are appended at the end delays the number of delays before the message is transmitted back Each delay is 50 milliseconds However the delay is made by a suspend 2 if the is being used Miscellaneous Functions void misticware char tbuf char count This is the gateway for RS 485 ninth bit protocol for binary communi cation The receive and the transmit buffers must already be set up Interrupt driven transmission must be intitialized tbuf the transmit buffer Data in the buffer should already be in the correct format count the number of bytes to be transmitted void optodelay This function produces a delay of 50 milliseconds The delay is implemented with a suspend 2 if the is being used Other wise it is a software countdown delay int rbuf there Monitors the receive buffer for a completed command or reply The function returns 1 ifa completed command or reply is available 0 ifa completed command or reply is not available void op send 21 char tbuf byte count This function is called by misticware to initiate transmission of data void op rec 21 This function is called by misticware to reset and to ready the receiver for data reception void op kill 21 Disables Z180 Port 1 The RS 485 driver
54. er unsigned int upper This function is the same as k item int but applies to unsigned integers e int fk item float char sl float num float lower float upper Displays modifies a floating point number using the five key system The term s1 is a printf format for displaying the number The format code should be in the form of n m The displayed line appears as follows VVVVVV WWWW YYYY where vvvvv is a prompt string wwww is chars long and yyyy is chars long The value must be at least 1 The sum m cannot exceed 9 The default is 6 and m 3 The term num is the floating point number to be displayed and or modified The arguments upper and lower are the upper and lower limits for the number This function will work for numbers in the ranges 1E6 1E 4 1E 4 1E6 with the appropriate format specification 60 The Five Key System Dynamic C 32 v 6 x int item enum char prompt int choice char s1 sn Allows the user to choose from a list of null terminated strings maxi mum 20 The string prompt must contain a string field code s or ns used to print the strings The last of the strings after s1 sn must be null The term choice returns the choice made by the user and is from 0 to n 1 Reading the Keypad without FK LIB The following program illustrates a way to read keystrokes without using FK LIB SRTK LIB The virtual driver is still required The fu
55. es 72 RS 232 Communication Dynamic C 32 v 6 x int getcrc char buffer byte count int accum Computes the CRC cyclic redundancy check or check sum for data in buffer Calls to getcrc can be concatenated to compute the CRC for a large buffer buffer is a pointer to characters for which to compute the CRC count is the number of characters in buffer limited to 255 for this function accum is the accumulated CRC value from previous computation The function returns the integer CRC value void resetZi80int This is a generic reset function that resets or disables interrupts for the DMA channels the Z180 serial channels 0 and 1 the programmable reload timers and CSIO and INT2 RS 485 Drivers Ifa serial port supports full duplex RS 485 communication the same drivers used for RS 232 communication may be used Just turn on RS 485 transmission according to the particular port For example to use Z180 Port 1 as an RS 485 port do the following outport ENB485 1 Dinit z1 Libraries Table 8 1 lists the Dynamic C libraries that support serial communication Table 8 1 Dynamic C Libraries Supporting Serial Communication Z0232 LIB Z180 Port 0 Z1232 LIB Z180 Port 1 S0232 LIB SIO Port 0 1232 LIB SIO Port 1 SCC232 LIB SCC Port A and B XP87XX LIB XP8700 PLCBus expansion board COM232 LIB ISA COM port MODEM232 LIB Accessory library used by all the preced
56. etimes fail if its worst case delay is 50 milliseconds waitfor Accuracy Limitations If an idle loop is used to implement a delay the processor continues to execute statements almost immediately within nanoseconds after the delay has expired In other words idle loops give precise delays Such precision cannot be achieved with waitfor delays Application Frameworks Costatements 31 A particular application may not need very precise delay timing Suppose the application requires a 60 second delay with only 100 milliseconds of delay accuracy that is an actual delay of 60 1 seconds is considered acceptable Then if the processor guarantees to check the delay every 50 milliseconds the delay would be at most 60 05 seconds and the accuracy requirement 1 satisfied Dependency Relations Among Costatements A program can contain a large number of costatements In general there will be groups of costatements that share the same loop or the same context Costatements in a second context that preempt costatements in the first context are restricted in how they can share data so special care must be paid to mutual communication among preempting tasks Costatements may be initially OFF initially ON or ALWAYS ON Those that are not always on can be turned on remotely even across preempting tasks The following code will start a remote costatement and wait for its completion costate CoBegin name waitfor isCoDone name
57. ey is pressed The current display is saved and each message string 1s displayed for 1 8 seconds then the previous display is restored The input should be an array of strings declared like this char hptr Str 1 Str 2 StrN The last string must be null The function returns nonzero if help is off and zero 1f help is on Application Frameworks The Five Key System 59 int fk item alpha char 51 char var int wdsize Modifies a string using the five key system The term s1 is a string containing a prompt The term var is the string to be displayed and or modified wdsize is the maximum length of the word string to be edited int fk item setdate struct tm time A five key function to modify the day month and year fields of a tm structure The term time is the structure to be modified int fk item settime struct tm time A five key function to modify the hour minute and second fields of a tm structure The term time is the structure to be modified int fk item int char string int num int lower int upper Displays modifies an integer number using the five key system The term string is a printf format having the form nu where n is one digit for example 5d The term num is the integer to be displayed and or modified The arguments upper and 1ower are the upper and lower limits for the number int fk item unsigned int char string un signed int num unsigned int low
58. eys 58 The Five Key System Dynamic C 32 v 6 x Special Key Combinations board resets when the menu key and certain other keys are held down simultaneously for more than 0 5 seconds The keys that work in these combinations all have sublabels to describe their actions These resets are described in Table 7 1 Table 7 1 PK2100 PK2200 Keypad Resets Key Strokes Result menu field Restart the program currently loaded setup run menu up Put the board in program mode with PC serial setup pgm 19 2 communications set to 19 200 baud menu down Put the board in program mode with PC serial setup pgm 28 8 38 4 communications set to 28 800 baud for the PK2200 and to 38 400 baud for the PK2100 The function k monitorkeypad described below detects these two key combinations Five Key Functions void fk monitorkeypad Monitors the keypad for keys pressed This function should be called as an SRTK high priority task It sets global variable k tkey to values from 1 to 12 depending on the key pressed The value is 0 if no key is pressed The function also monitors for the 2 key reset combination If a reset combination is detected the function will not return but will force a watchdog time out There is no buffer Key presses should be pro cessed within 100 milliseconds or they will be lost int fk helpmsg char hptr Displays a series of help messages when the HELP k
59. functions 72 service routines 72 79 vector table 72 ISA COM ports 66 Index 97 isCoDone 30 isCoRunning 0 2222 30 ITEM 56 DX register seis 47 K kernel real time 17 39 42 43 48 70 72 78 88 keyboard see Five Key system 55 56 63 75 L lastlocADDR 27 27 laten CY 14 LCD see Five Key system 55 56 63 75 34 master message format 76 T7 master slave command protocol 76 networking 79 81 serial communication 77 78 software support TI memory extended uploaded data 70 random access 53 54 MENU 56 misticware 78 modem commands 71 deciphering 71 modem communication 67 checking for commands 72 delayed 72 restarting nias 72 98 Index multitasking 16 44 16 17 preemptive 16 17 18 priority levels 18 shared variables 17 18 N WATCHDOOG 39 40 nested costatements
60. if expression evaluates false zero the reentry point for the costatement is set at the waitfor statement and the program jumps out of the costatement Then the program evaluates the waitfor expression each time it reenters the costatement If the expression 1s false the program jumps out again If the expression 1 true nonzero the program continues with the statement following the waitfor Delay Functions Three special functions others can be added allow delays to be used in the expression evaluated by a waitfor int DelaySec unsigned long seconds int DelayMs unsigned long milliseconds int DelayTicks unsigned int ticks Thus expressions such as the following can be used wait for 30 minutes waitfor DelaySec 30L 60L wait for device or 40 milliseconds waitfor DelayMs 40L device ready These delay functions depend on the virtual driver Initialize the virtual driver with a call to VdInit before they can be used eu See Chapter 4 The Virtual Driver yield A costatement can yield to other costatements The yield statement 1 permitted only inside a costatement yield The yield makes an unconditional exit from a costatement Application Frameworks Costatements 29 abort A costatement can terminate itself using the abort statement permitted only inside a costatement abort The abort statement in effect causes the execution to jump to the very end of the costatement wher
61. ing libraries Application Frameworks RS 232 Communication 73 Sample Programs Table 8 2 lists sample programs that illustrate serial communication Table 8 2 Dynamic C Serial Communication Sample Programs RS232 C Simple RS 232 communication using the Z180 Port 0 7180 Port 0 of a PK2100 XP87XX C Simple RS 232 communication with the XP8700 PLCBus expansion board 21232 Simple RS 232 communication using the 7180 Port 1 5 232 Simple RS 232 communication using SCC Ports A and B DOWNLOAD C RS 232communication for monitor program using the The programs in Table 8 3 use the serial port as a diagnostic port Except for 21 and SCCREM C these programs are also the master programs that can talk to a slave running or CSREMOTE C via the RS 485 half duplex linkage Table 8 3 Dynamic C Sample Programs RS 232 communication with Z180 Port 0 ZOREM C Z1REM C RS 232 communication with Z180 Port 1 SOREM C RS 232 communication with SIO Port 0 SCCREM C RS 232 communication with SCC Ports A and B UARTREM C RS 232 communication with the XP8700 PLCBus expansion board CZOREM C RS 232 communication with the Z180 Port 0 for the PK2100 and the PK2200 CUARTREM C RS 232 communication with the XP8700 PLCBus expansion board 232 Simple RS 232 communication for ISA COM Ports 1 and 2 COMIREM C RS 232 communication with
62. is more complex and somewhat harder to use and the old system runs only with the full real time kernel RTK not the simplified real time kernel SRTK With the old 5 key system the ADD and DELETE keys can be used for an extended five key system where menu items can be added or deleted while a program is running The old 5 key system also supports up to four alarm functions The old 5 key menu server operates as a task running under the real time kernel The menu server can either be code driven or linked list driven The code driven technique 1 more flexible but the linked list method is easier to use Code Driven Approach In the code driven approach the programmer creates menus for updating parameters A real time kernel task calls all the menus repeatedly Each menu handles its own list of items The following examples shows a conceptual code driven menu system main initialization background indirect background request TASK1 while 1 indirect taskl the code driven menu server while 1 menul optional menu 1 housekeeping 2 continued 88 Old 5 Key System Dynamic C 32 v 6 x int menul int k while 1 _5 parameter optional housekeeping for parameter 1 if MENU return 5key parameter2 menu key pressed optional housekeeping for para
63. itfor ex pression costatement can as many statements including abort statements yield statements and waitfors as needed Costatements may be named or unnamed The name of a named costate ment can be one of the following Avalid C name not previously used This results in the creation of a structure of type CoData of the same name The name of a local or global CoData structure that has already been defined A pointer to an existing structure of type CoData If name is missing then the compiler creates an unnamed structure of type CoData for the costatement State The term state can be one of the following always costatement is always active Unnamed costatements are always on init costatement is initially on and will automatically execute the first time it is encountered in the execution thread The costatement becomes inactive after it completes or aborts If state is absent the costatement is initially off The software must trigger the costatement for the costatement to execute Then it will execute once and become inactive again Unnamed costatements are always on The CoData Structure Each costatement is associated with a structure of type CoData For this discussion assume that each costatement corresponds to a static CoData structure Application Frameworks Costatements 25 This is the CoData structure typedef struct
64. its capacity If the device with which the controller is communicating does not support CTS and RTS the CTS and RTS lines on the controller side can be tied together to make communication possible XMODEM File Transfer Z World supports the XMODEM protocol for downloading data from and uploading data to a controller Currently the library supports download ing an array of data whose size is a multiple of 128 bytes Uploaded data are written to specified area in RAM The targeted area for writing should not conflict with the current resident program or data serial driver is put into BINARY mode during XMODEM transfer Character echo 1s suspended Modem Communication Modems allows RS 232 communication across long distances using telephone lines If the modem option is selected character streams that are read from the receive buffer are automatically parsed for modem com mands If a modem command is found appropriate actions are taken Normally the communication package would be in COMMAND mode while waiting for valid modem command or messages Once a link is established communication goes into DATA mode that 1 regular RS 232 communication In DATA mode the modem is still monitored for a NO CARRIER message The software assumes that modem commands for which it scans are terminated with CR carriage return or ASCII 0x0D Therefore the modem option 1 easiest to use when the protocol also has CR as the terminating
65. me time The address of the current starting point in the costatement and the time at which the currently running delay if any began are saved in the data structure A costatement can be thought of as a local computer with its own instruc tion counter One or more statements are executed in the costatement on each pass of the execution thread Costatements are cooperative concurrent tasks because they can suspend their own operation There are several ways they do this They can waitfor events conditions or the passage of time They can yield temporarily to other costatements They can abort their own operation Costatements can also resume their own execution from the point at which they suspended their operation In general each costatement in a set of costatements is in a state of partial completion Some are suspended some are executing With the passage of time all costatements should suspend and then resume All costatements in the program except those that use pointers as their names are initialized whenever the function chain GLOBAL INIT is called The functions VdInit and uplc init also call GLOBAL INIT See Chapter 4 Virtual Driver and the CPLC LIB library in the ev Dynamic C Function Reference manual for more information 24 Costatements Dynamic C 32 v 6 x Costatement Functions Syntax The general format of a costatement appears below costate name state statement yield abort wa
66. meter WATCHDOGS which defaults to 10 Create virtual watchdogs with the function wd VdGetFreeWd count This function enables a new virtual watchdog starts it counting at count and returns an integer ID Make count greater than 1 because otherwise the watchdog will reach zero and time out on the first decrement Once a virtual watchdog is created it must be hit periodically so it does not time out and reset the system Hits are needed by all the virtual watchdog timers To hit the virtual watchdog use the function VdWdogHit int wd Hitting the watchdog resets its count to the count value with which it was created To release the virtual watchdog wd use the function VdReleaseWd int wd Global Initialization When the virtual driver is initialized with VdInit the driver calls GLOBAL INIT which executes all the GLOBAL INIT function chain segments in the program and libraries This results in the initialization of the entire program The GLOBAL INIT segment must appear after the variable declarations and before the executable statements The initialization statements placed GLOBAL INIT segment can be complex C assembly code with loops branches and function calls or they can be simple assignments whatever is required by the code The _GLOBAL_ INIT segment can take action to precondition all or part of the hardware as well as to preset variable data Dynamic C treats a variable initialized with
67. meter 2 if MENU return _5key parameter3 menu key pressed optional housekeeping for parameter 3 if MENU return menu int 2 code here int menuN code here Linked List Approach key pressed The following code shows the linked list approach The library function 5key menu is called from a real time kernel task This function uses the linked lists that were created during initialization with calls to _5key_setmenu The linked list method handles parameters easily but there is no way to do housekeeping for specific parameters or menus main initialization routines 5key setmenu 5key setmenu 5key setmenu 5key setmenu 5key setmenu 5key setmenu 5key setmenu 5key setmenu 5key setmenu background menul menul menul menu2 menu2 menu2 menu3 menu3 menu3 indirect background request TASK1 while 1 indirect taskl 1 parameter2 parameter3 parameter4 parameter5 parameter6 parameter7 parameters parameter9 Ne Ne Ne Ne Ne Se gt e 2 vs 4 _5 menu endless 5 service eo Application Frameworks Refer to the Dynamic C Function Reference manual for more information on function use Old 5 Key System 89 Updating and Monitoring Parameters The old system support
68. mic 32 v 6 CHAPTER 3 COSTATEMENTS Costatements allow cooperative multitasking within an application Costatements are blocks of code that can suspend their own execution at various times for various reasons allowing other costatements or other program code to execute Costatements operate concurrently There are several advantages such as the following to using costatements Costatements are a feature built into the language e Costatements are cooperative instead of preemptive Costatements can operate without multiple stacks Using costatements effectively requires knowledge of their syntax their supporting data structures and the mechanisms by which they may be put to use Chapter 3 discusses the following topics Solving problems with costatements Costatement functions Costatement topics timing dependency nesting and errors Application Frameworks Costatements 21 Solving Problems with Costatements Costatements are Z World s extension to C to facilitate cooperative multitasking The following example shows how to use costatements to simplify the solution to a real time problem Example The following sequence of events is common in real time programming Start 1 Wait for a push button to be pressed Turn on the first device Wait 60 seconds Turn on the second device Wait 60 seconds Turn off both devices Go back to the start The most rudimentary way to perform this functi
69. n 67 72 _5 91 92 _5 _ 89 92 _5 setalarm 92 _5 _ 91 _5 setmenu 89 92 _5 setmsg 91 _ALARM1 ALARMA 92 GLOBAL INIT 24 27 40 prot Init nadie 54 prot recover 54 SKEY LIB inet 88 92 SKEYEXTD LIB 88 A abort 24 25 27 30 33 35 ADD key eene 56 57 alarm functions 88 always on 25 27 35 assembly language 15 B background task RV 42 battery backed RAM 53 54 baud rate 12 67 77 BINARY mode 65 BIOS ecce accede det 53 buffer 68 69 77 78 Initialization 67 POAGING etim 68 transmit 69 78 Initialization 67 writing esses 68 69 Application Frameworks INDEX COVED scabini 53 54 check sum 76 77 78 computing 73 check opto command TI checking for modem commands 72 ChkSum nemen 27 CHKSUMZ 27 CoBegin 26 27 30 nte 25 28 30 description 25 26 27 initialization 24
70. n endless loop so the hardware watchdog times out Multiple virtual watchdog timers allow a programmer to create more robust error handlers by monitoring several different tasks separately for missed execution Reset and Super Reset A reset because of a power failure a software failure or a watchdog time out causes the program counter to be reset to 0000 The Dynamic C BIOS restarts the program automatically in these cases Z World s super reset is a mechanism to initialize certain data in battery backed RAM which should be retained after a normal reset super reset always occurs after a program 1 first loaded It is therefore necessary to distinguish whether the program is starting from scratch during a genuine start up or is recovering from a failure If it is a genuine start up the program must initialize its variables If recovering from a failure the program should recover critical data from before the failure Certain controllers have the helpful ability to determine whether the crash occurred because of a power fail or a watchdog time out Even so a more general approach is necessary to detect these and other kinds of failures For this purpose then the Dynamic C compiler places a time stamp in each program The time stamp 15 passed as an argument to main It is highly unlikely that two programs would ever have the same time stamp Thus when a program is starting up the first time assume that the previ ous program whate
71. n is declared with the keyword firsttime A proper firsttime function definition would look like this firsttime int MyDelay CoData ptr delay params some code The first argument of a firsttime function must always be a pointer to a CoData structure A firsttime function will use this pointer to check whether the costatement s firsttime field is 1 If so the function will set up variables required to count the delay The firsttime function should also set the firsttime flag to 0 so subsequent visit to the waitfor do not reset the delay counter Calling a First Time Function From within a costatement use a firsttime function as an argument to a waitfor statement costate waitfor MyDelay 1000 Note that the call to MyDelay has only one parameter The CoData pointer required in the function definition is not to be included in the call The compiler automatically passes the address of the CoData structure as the first argument if a firsttime function is called from within a costatement 28 Costatements Dynamic C 32 v 6 x Associated Keywords Functions waitfor A costatement can wait for an event a condition or the passage of a certain amount of time For this purpose there is the waitfor statement permitted only inside a costatement waitfor expression The waitfor suspends progress of the costatement pending some condition indicated by expression When a program reaches waitfor
72. n this case It is not possible to do any further debugging through Dynamic C once the service routine has taken over For communication with a serial device other than the Dynamic C pro gramming port on the PC the program has to make sure that the hardware is properly configured before sending any serial messages For example when using the Z180 s Port 0 for serial communication with a modem the keypad PK2100 or PK2200 only may be used to trigger the initialization of the serial port Without such a trigger the modem might not communi cate with the support software properly because the initialization routine also send commands to the modem to initialize it When executable programs are generated for the EPROM or for download to RAM there will be no need for communication with Dynamic C The compile time directive SINT VEC can then be used freely RS 232 Software int Dinit 20 void rbuf void tbuf int rsize int tsize byte mode byte baud byte modem byte echo Initializes Z180 Port 0 for communication rbuf pointer to the receive buffer tbuf pointer to the transmit buffer rsize size of the receive buffer tsize size of the transmit buffer mode selects the operation mode as follows bit 0 0 1 stop bit 1 2 stop bits bit 1 0 parity 1 with parity bit 2 0 7 data bits 1 8 data bits bit 3 parity 1 parity bit 4 O CTS RTS off 1 RTS enabled Application Frameworks RS 232 Communication 67
73. nction lc kget is found in LCD2L LIB It detects and responds to 2 key reset combinations duse vdriver lib int key main VdInit for if key 1 kget 0 0 printf key d n key Application Frameworks The Five Key System 61 62 The Five Key System Dynamic C 32 v 6 x 8 RS 232 COMMUNICATION Z World supports RS 232 communication with function libraries for the various serial ports found in Z World controllers and their accessories Chapter 8 discusses the following topics Serial communication Function libraries and sample programs Application Frameworks RS 232 Communication 63 Serial Communication Z World supports RS 232 communication with function libraries for the following ports Z180 Ports 0 and 1 SIO Ports 0 and 1 on the BL1100 SCC Z80C30 Ports A and B on the BL1300 The XP8700 expansion card The functional support for serial communications consists of the follow ing Initialization of the serial ports Reading data from the receive circular buffer Writing data to the transmit circular buffer The RS 232 packages have the following features Circular send and receive buffers serviced with serial interrupts Echo option CTS RTS control XMODEM protocol for downloading and uploading data Modem option Send and Receive Buffers Serial communication is made easier with a background interrupt routine updating the send and
74. o generate the delay void Ddelay 100ms Creates a 100 millisecond delay approximately void reload vec int vector int function Load the address of an interrupt service routine ISR into the vector table This function 15 useful during program development when either of the Z180 Port 0 Z0 or the PLCBus XP8700 UART 3 1 used as the Dynamic C programming port It is also useful as a safeguard against the BIOS rewriting the ZO or INT1 PLCBus UARTS vector when the controller is powered up or reset into programming mode as occurs when using the Program Loader Utility PLU to update the controller s application either via port Z0 or PLCBus UART 3 If the application uses the Z0 or PLCBus UART serial ports it should call reload vec once each for the used ZO or PLCBus ISRs early in its normal initialization to ensure that the respective vectors point to its ISRs For other serial ports use the compile time interrupt directive INT_VEC to load the ISR address into the interrupt vector table when generating the executable code for EPROM or for download to RAM vector is the offset for the specific interrupt function is pointer to the interrupt service routine Since Dynamic C 32 v 6 30 reload vec updates the vector only when different from the current vector Avoid repeatedly updating a vector with different ISR addresses on a Flash EPROM equipped controller since the Flash EPROM has a maximum life of about 10 000 writ
75. om the master Slave prints the master s message to STDIO and also replies to the master char rbuf 255 receive buffer char query 40 query buffer char reply 40 xeply buffer main int j VdInit initialize for 19200 baud receive buffer slavel op init 21 16 rbuf 1 j 1 while 1 runwatch if masterquery query check for master query sprintf reply s Slave Reply d query 344 sends back reply to the master replyOpto22 reply strlen reply 0 check for master query copy message from the master to query if it s valid int masterquery char query int i if check opto command 1 return 0 for i 0 i rbuf 1 2 1 query i rbuf 2 i query i 0 put an end of string return 1 Note that sendOp22 just sets up the message for transfer using the ninth bit protocol It does not poll for the completion of the transfer All transfers of messages are done in the background interrupt routine 80 Master Slave Networking Dynamic C 32 v 6 x Libraries and Sample Programs Libraries Table 9 1 lists the Dynamic C libraries that support master slave communi cation Table 9 1 Dynamic C Libraries That Support Master Slave Communication NETWORK LIB Half duplex RS 485 communication drivers MODEM232 LIB Accessory library used by preceding libraries Sample Programs Table 9 2 list
76. on is to idle busy wait in a tight loop at each of the steps where waiting is specified But most of the computer time will used waiting for the task leaving no execution time for other tasks Figure 3 1 shows the execution of this task schematically Figure 3 1 Execution of Sequence of Tasks in a Program If there are other tasks to be run this control problem can be solved better by creating a larger loop that processes a number of tasks Now each task can relinquish control when it is waiting thereby allowing other tasks to proceed Each task then does its work in the idle time of the other tasks This situation 1 like that of a worker who goes from station to station performing jobs according to an instruction book at each station By traveling from station to station the worker can execute long sequences of jobs without having to waste time at any station waiting for the next event 22 Costatements Dynamic C 32 v 6 x This 1 similar to a cook who has 5 to 10 ovens and many cook pots to prepare many different meals at the same time Solving Problems Without Costatements One way to implement multitasking 1 with state machines A state machine is a programming construct that goes through a sequence of states the states being indexed by the value of one or more variables Here 1s what a state machine solution might look state 1 initialization for other tasks or state machines The variable time is
77. opied to buffer The terminating character 1 discarded and the message in buffer is terminated with a null character according to the C convention The function returns 0 no message found with the specified terminating character message has been successfully extracted from buffer 68 RS 232 Communication Dynamic C 32 v 6 x int Dwrite 20 char buffer int count Copies count bytes from buffer to the transmit buffer If the transmit buffer 1 not already transmitting the function initiates transmission It returns 0 transmit buffer did not have space for count bytes Write 15 successful e void DzOsend prompt Places CR and gt in the transmit buffer e void Dreset zOrbuf Resets the receive buffer e void Dreset zOtbuf Resets the transmit buffer and stops transmission void Dkill 20 Disables Z180 Port 0 Sample Program This example shows RS 232 communication between a controller and a PC functioning as dumb terminal define CR OxOd carriage return char baud 8 9600 baud divided by 1200 char mode 4 1 stop bit no parity 8 data bits char ismodem 0 no modem is connected char isecho 1 data received ar choed char tbuf 384 circ transmit buffer char rbuf 200 circ receive buffer main char buf 20 messages Dinit z0 rbuf tbuf 200 384 mode baud ismodem isecho DzOsend prompt send a prompt while 1 wait for a
78. pplication Frameworks Real Time Kernels 43 The following example shows how program might look with and without the virtual driver define NTASKS 4 define RUNKERNEL 1 use RTK LIB the four task prototypes int heater pump sensor backgnd array of 4 task pointers int Ftask 4 heater task 0 pump task 1 sensor task 2 backgnd task 3 WITH VIRTUAL DRIVER main VdInit initialize VD and RTK run every 0 5 run task0 every 5 ticks run every 1 15 run taskl every 15 ticks run every 2 100 run task2 every 100 ticks backgnd the lowest priority task WITHOUT VIRTUAL DRIVER eke DI disable interrupts init kernel initialize kernel run every 0 5 run every 1 15 run every 2 100 init timer0 9216 set timer interrupts 50Hz EI enable interrupts backgnd The program can request that a task be invoked at a particular time 48 bit time in ticks or after a certain delay 32 bit count in ticks or that the task be invoked every nn ticks nn being a 16 bit number A task that 1s running can also request that its own execution be suspended for up to m ticks 16 bit number Any task or interrupt routine can also request that another task be run at the first opportunity The RTK multitasking capability may be used as a tool to separate control loops into independent functions
79. quency of Timer 1 7180 on chip timer Consequently changing the frequency of Timer 1 would change the timing charac teristics of the SRTK Gu Refer to Chapter 5 Real Time Kernels for further details Application Frameworks Real Time Programming 17 Tips for Multitask Programming Assign Priority Levels Determine which operations must be performed within a fixed amount of time For example if a controller grips a falling object after the object passes a sensor the grip action must be initiated and performed in time so that the object is caught If the same system has a liquid crystal display LCD to display the time the gripper routine should get higher priority than the LCD routine Generally the tighter the deadline the higher the priority Lower priority tasks are the ones that can be interrupted preempted Their completion can be delayed by a preempting task Tight deadlines do not imply high frequency The falling object may arrive once in an hour or at random The LCD should be updated every second but the gripper routine still must have a higher priority Identify Shared Variables In a real time system with concurrent tasks that share data subtle problems can occur with variables that are stored and fetched in a nonatomic manner When several instructions are necessary to fetch or store the variable an interrupt can occur between the instructions For example a floating point variable occupies four
80. receive buffers for serial communication Every time a new character is received it is put into the receive circular buffer The receive buffer can be read one character at a time or as a stream of characters terminated with a special character Data are sent by writing to the circular transmit buffer If the serial port is not already transmitting Z World write functions will automatically initiate transmission Once the last character of the buffer has been sent the transmit interrupt 1 turned off Data may be written one character at a time or as a stream of characters Echo Option Ifthe echo option 1s selected when a serial port is initialized any character received is automatically echoed transmitted back This feature is ideal for systems with a dumb terminal and for checking transmitted characters With or without echo the serial drivers automatically parse out the BACK SPACE character ASCII 0x08 separate function call after initialization of the serial port can put the serial drivers in BINARY mode that is all data are placed in the serial receive buffer 64 RS 232 Communication Dynamic C 32 v 6 x CTS RTS Control If the CTS RTS option 15 selected the support software will pull the RTS line high when the receive buffer has reached 80 of its capacity Thus the transmitting device if its CTS 1 enabled will stop transmitting The software pulls the RTS line again when the received buffer has gone below 20 of
81. s 1oat values integer values 1 ean values and time and date character strings Parameters can be modified or monitored under the five key system When data are moni tored they are presumed to be modified somewhere else in the program Their values are displayed when changed Each data type 1 serviced with a different function call but the functions are similar to one another In the following example let the float parameter Tb boiler temperature be used for setting the temperature of a steam boiler These declarations apply define MODIFY 1 define NOT MODIFY 0 define DISPLAY 1 define NO DISPLAY 0 define RTCLK 0 10 define RTCLK 0 00 define NO HELP char 0 define NO FUNCTION int 0 float Tb char Tb help Tb is the temperature of boiler 3 Use UP DOWN and FIELD keys to modify Code Driven Approach The function call to change the variable Tb would be 5key float Tb amp Tb 300 00 100 00 Tb help sizeof Tb help MODIFY 10 or if the variable is simply monitored 5key float Tb amp Tb 300 00 100 00 Tb help sizeof Tb help NOT MODIFY 10 The following declarations are needed for a string time that displays and allows changes to the real time clock char time 9 char time help time display and set the real time clock j The function call would be the following _5key_time time time time help sizeof time help
82. s the major RTK routines BEGIN run timer Step timer48 48 bit timer BEGIN task loop IF task has non zero suspend count Decrement count and set task request when count becomes zero ENDIF CASE operation mode run at Set task request flag run after Set task request flag run every Set task request flag ENDCASE END task loop call rkernel to invoke next task END run timer BEGIN rkernel IF blocked return with block entry to kernel BEGIN task loop high priority first IF task is running return from kernel IF task is requested Set task running and resume execution of task Return or suspend Clear request flag ENDIF END task loop Execution never gets here Background task will run instead END rkernel 48 Real Time Kernels Dynamic C 32 v 6 x sample program SAMPLESNDEMO in Dynamic C demonstrates the use of the real time kernel without the use of the virtual driver The demo program has several tasks which are used as follows Task 1 simulates a tank of liquid holding 1000 liters of liquid When the level in the tank 15 low the eve flag 1s turned on The level flag 1 equivalent to a mechanical level sensor on a physical tank When the intake flag is on 25 liters of liquid enter the tank each tick Ten liters leave the tank every tick If the heater flag is on the temperature of the tank increases 1 C every tick The liquid entering the tank has a temperature of 20 C Task 1 runs ever
83. s the sample programs that illustrate master slave communi cation Table 9 2 Dynamic C Sample Programs for Master Slave Communication RS485 C Simple slave RS 485 program Talks back to master board running RS232 C SREMOTE C Diagnostic port via the RS 485 linkage The master has to be running one of the following programs ZOREM C UARTREM C CZOREM C CUARTREM C SOREM C COMIREM C or COM2REM C PK2100 or the PK2200 Same as SREMOTE C but will only run on the Application Frameworks Master Slave Networking 81 82 Master Slave Networking Dynamic C 32 v 6 x Is ArPENDIX A EXECUTION SPEED Application Frameworks Execution Speed 83 Table 1 lists the execution times of various arithmetic operations Z World controllers have clocks frequencies ranging from 6 144 to 18 432 MHz Table A 1 Execution Times of Arithmetic Operations us PSI Clock Frequency MHz 6 144 9 216 12 288 18 432 16 bit integer add 2 7 1 8 1 4 0 9 16 bit integer multiply 24 16 12 8 16 bit integer divide 142 5 95 72 475 Long 32 bit integer add 21 14 10 5 7 Long integer multiply 123 82 60 5 41 Long integer divide 609 406 304 5 203 Floating point 32 bit add or subtract 117 78 19 5 39 Floating point multiply 171 114 85 5 57 Floating point divide 429 286 214 5 143 Sine or cosine 4650 3100 2325 1550 Square root 1275 850 63
84. s to help the user solve these problems Application Frameworks Real Time Programming 15 Multitasking A task 1s an ordered list of operations to perform In a multitasking environment more than one task each representing a sequence of opera tions can appear to execute in parallel In reality a single processor can only execute one instruction at a time so the parallel tasks execute almost in parallel If an application has multiple tasks to perform multitasking software can usually take advantage of natural delays each task to increase the overall performance of the system Each task can do some of its work while the other tasks are waiting for an event or for something to do Although multitasking may actually decrease processor throughput slightly it is an important concept A controller is often connected to more than one external device A multitasking approach makes it possible to write a program controlling multiple devices without having to think about all the devices at the same time In other words multitasking is an easier way to think about the system There are two types of multitasking available for developing applications in Dynamic C preemptive and cooperative Cooperative Multitasking In a cooperative multitasking environment each task voluntarily gives up control so other tasks can execute A kernel is not required in this case because the tasks cooperate among themselves If periodic task scheduling
85. t time2 void gettimer void time Returns the current 48 bit time to the 6 byte area to which time points void run after int tasknum long delay Requests the kernel to run the task specified by tasknum after delay ticks have occurred void run every int tasknum int period Requests the kernel to run the task specified by tasknum every period ticks The first request comes after period ticks This 1 exact and no ticks will be gained or lost in the period void request unsigned int tasknum Requests the kernel to run the task specified by tasknum immediately If a request for the task is pending this call has no further effect The specified task will be run on a future tick when priorities allow void run cancel int tasknum Cancels any pending requests for the task specified by tasknum void suspend unsigned int ticks This routine must be called only from within a given task It allows the task to suspend itself for the specified number of ticks after which it will continue to be requested automatically Execution resumes at the statement following the call to suspend 46 Real Time Kernels Dynamic C 32 v 6 x If ticks 15 0 then the suspension 15 for an indefinite period of time until the task is again requested by some outside agent such as a call to run every Using a while statement is the usual method of using suspend to wait for an external event while event suspend 20 This ex
86. te address However the IX register will be incorrect on return to the function that called the suspended function This is because the IX register 1s saved on the stack on function entry and restored on function exit If the function suspends then the restored IX register will usually be incorrect This can cause the following two types of problems 1 Invalid pointers to auto variables or function arguments 2 Fatal errors from the stack corruption check Application Frameworks Real Time Kernels 47 If stack corruption checking is enabled false stack corrupt messages can occur because these routines use the IX register to access the stack information on a return statement Stack corruption checking can be disabled globally using the COMPILER OPTIONS command on the OPTIONS menu Stack checking can also be disabled by means of the nodebug keyword in the function declaration Problems with suspend are avoided by not using pointers to auto variables or arguments belonging to the task and by following one of these rules 1 Call suspend only from a root task not a subfunction 2 Call suspend only from the main program and from first level subfunctions and do not use any auto variables in the root task Disable stack corruption checking for the main routine auto variables may be used in subroutines as long as the number of bytes used for these variables is less than TASKSTORE SIZE RTK Internals The following pseudocode show
87. teger unsigned time string and date string An enumerated parameter acts as a menu allowing the user to choose from a list of choices identified by user defined strings The five key system continues to operate and respond to key presses while it displays messages or parameter values Ask for help using the HELP key on any five key menu or param eter 56 The Five Key System Dynamic C 32 v 6 x Programmer Features A programmer may extend the five key system in these ways Write code to use the F1 F2 F4 add del keys Provide help messages via the HELP key The five key system 1 programmed in the following way 1 Initialize the virtual driver and simplified real time kernel SRTK 2 Call k monitorkeypad from the high priority SRTK task 3 Follow the model shown in the sample code below to define menu titles prompts and menu items in the SRTK low priority task or a function called by it Sample Code The following code shows how a program using FK LIB might appear Refer to the Dynamic C sample program SAMPLES FKEY FKSAMP C for a complete sample program SAMPLE PROGRAM duse srtk lib duse fk lib duse vdriver lib nointerleave define RUNKERNEL 1 float f int i unsigned int u char strng 11 main strcpy strng abcdefghi 25 34 1 15 u 5 VdInit SRTK needs virtual driver init srtkernel initialize the SRTK up beepvol 1 needed for PK2
88. th Dynamic C supports prioritized preemption only tasks of a higher priority can interrupt tasks of lower priority As many priority levels as needed can be created when using the RTK The RTK also has a suspend function for a high priority task to suspend itself for a specified length of time or until awakened by other tasks so that lower priority tasks can execute The suspend function helps a task to be cooperative Z World also ships a simplified real time kernel SRTK Like the full RTK the simplified RTK is prioritized and preemptive However there are only three levels of priority in the SRTK The top priority task executes at 25 millisecond intervals the low priority task executes at 100 millisecond intervals and background processing even lower priority can execute when no other tasks are executing There is also a fast call task available with either kernel or when no kernel is running to execute as often as 1280 times per second The fast call task preempts all other tasks The fixed properties of the SRTK make it compact and easy to use The SRTK can combine with cooperative multitasking costatements to provide a robust multitasking environment A timer interrupt handler may have to be written if a higher frequency is desired Assuming the interrupt handler has about 100 instructions the maximum frequency of timer interrupts could be about 6 10 kHz on a 9 MHz board Note that the SRTK depends on a fixed fre
89. the XP8700 and XP8800 User s Manual for further details on the XP8700 expansion card The function names for these ports incorporate the following keys Port Key Port Key Z180 Port 0 20 SIO Port 0 50 7180 Port 1 21 SIO Port 1 s1 SCC Port A sca ISACOM1 comi SCC Port B scb ISACOM2 com2 XP8700 uart For example the initialization routine for Z180 Port 0 is called Dinit_z0 and is described here The same function for SIO Port 0 is named Dinit_s0 The equivalent function for the XP8700 expansion card is Dinit_uart The equivalent function call for SCC Port B is Dinit_scb The equivalent function call for ISA Port 2 is Dinit_com2 Each function described for z0 in this section has eight other functions that use the other keys in their names 66 RS 232 Communication Dynamic C 32 v 6 x Interrupt Handling Normally the serial interrupt service routine 1 declared with this compiler directive INT VEC SERO VEC routine name However if the same serial port is used for Dynamic C programming and for communication the program has to be downloaded first through Dynamic C before the address of the serial interrupt service routine 1s loaded into the interrupt vector table Put simply the service routine must be loaded at run time The function void reload vec int vector int function will load the address of the service routine function into the specified location in the interrupt vector table Do not use the INT_VEC directive i
90. the baud rate in multiples of 1200 specify 16 for 19 200 baud rbuf the receive buffer address the network address of the board 0 for the master board 1 255 for slaves int check opto command Checks for a valid and completed command or reply in the receive buffer The function returns with 0 ifthere is no completed command or message available 1 ifthere is a completed command or reply available 2 if the completed command or reply has a bad CRC check int sendOp22 byte dest char message byte len int delays The master sends a message to the slave and waits for a reply The function puts the message in the following format slave id len 1 CRC hi CRC lo The parameters are identified below dest the slave destination 1 255 message the message len the length of the message The maximum message length is 251 bytes delays the number of delays to wait for the slave reply Each delay is 50 milliseconds However if the is in use the delay is made by a suspend 2 The function returns if there is no reply from the slave 2 if a completed reply has a bad CRC 1 if there is a completed reply with a proper CRC The slave s reply 15 stored in the receive buffer initialized with op init zl Application Frameworks Master Slave Networking 77 void replyOpto22 char reply byte count int delays The slave replies to the master s inquiry The function puts the r
91. tive and define VD FASTCALL 1 has been declared a vd quick loop function will be called every nn clock interrupts The programmer is expected to provide the vd quick loop function If the function is not provided the virtual driver will call a dummy routine The term nn is a number from 0 to 255 defined by vd initquickloop nn as shown in the calling sequence If nn 0 then FASTCALL is turned off If nn 1 vd quick loop is called 1280 times per second If nn 255 vd quick loop is called 5 times per second Call vd initquickloop after VdInit otherwise nn will be reset to zero FASTCALL may be used with both the RTK and the SRTK and without ei ther The vd quick loop function will preempt the highest priority tasks in either kernel FASTCALL provides a method for running very fast tasks that must have response times on the order of a few milliseconds or that need to be invoked as continuations of interrupt routines The function DelayTicks has a waitfor granularity of less than a millisecond Application Frameworks The Virtual Driver 39 Virtual Watchdog Timers The virtual driver has a scheme for establishing any number of indepen dent watchdog timers in software Each virtual watchdog is a byte that 1s decremented every 25 milliseconds If any virtual watchdog reaches zero the virtual driver deliberately times out the hardware watchdog causing a hardware reset The maximum number of virtual watchdogs is set by the para
92. tively minor since they are simply the overhead from processing interrupts More serious delays occur when interrupts are disabled when an interrupt is requested Interrupts can be disabled for example during critical sections of code Interrupt process ing itself disables interrupts until the interrupt service routine reenables them or exits If software turns off interrupts for 25 microseconds and an interrupt request happens just as the interrupts are disabled the interrupt service will be delayed for an additional 25 microseconds 14 Real Time Programming Dynamic C 32 v 6 x A running program will fail if the interrupt latency 1 too great For example if the serial port is receiving characters every 173 microseconds 57 600 baud then an interrupt latency of 2 x 173 us 347 microseconds will cause a lost character because the serial port can only hold two characters before it loses one Interrupt routines are usually most efficient when written in assembly language but interrupt routines can be written in Dynamic C at the expense of a minimum overhead of about 25 microseconds on a 9 MHz processor which is the time necessary to save the registers If the service routine leaves interrupts off for its duration then it is necessary to add another 30 microseconds to the latency calculation to allow for the return from interrupt plus the amount of time it takes to execute the routine The advantage of assembly language routines is th
93. uilt on each pass of the execution thread For example the following nested costatements might be involved in outputting data to a user terminal costate X outermost level waitfor printmenu printmenu costate Y intermediate level waitfor cursorpos cursorpos costate Z innermost level waitfor sendstring In this example the outermost costatement X waits for a lower level routine to print a menu The printmenu routine in turn waits for a cursor positioning routine which in turn sends a string to the terminal and waits for the completion of sendstring Since costatements are used at each level the function nest is rebuilt and torn down on each pass of the execution thread However the reentry position at each level for each costatement 15 held in static storage If the sendstring routine runs into trouble a 1ongjmp may provide an appropriate escape The setjmp and longjmp would be structured as follows this case in the global declarations jmp buf savreg storage for longjmp in your highest level function if setjmp savreg code to recover from error CoReset amp Z terminate sendstring CoReset amp Y terminate cursorpos CoReset amp X terminate printmenu 34 Costatements Dynamic C 32 v 6 x the call to the nested costatements costate X waitfor printmenu args somewhere in your code will be an error exit if
94. ul transfer 2 canceled transfer canceled by sender side Miscellaneous Functions int Dget modem command Deciphers a Hayes compatible modem command The function returns if no modem command is matched The modem commands are summarized below 0 WXnOK okay respond 1 MnCONNECT connect at 300 baud 2 NAnRING ring detected 3 XnNO CARRIER no carrier 4 AnERROR command error 5 XnCONNECT 1200 connect at 1200 baud 6 AnNO DIALTONE no dial tone 7 MAnBUSY line busy 8 ANSWER no answer 9 AnCONNECT 2400 connect at 2400 baud 10 Wn just a line feed A Hayes Smart Modem compatible is recommended A NULL modem is needed between the PK2100 and the modem Some modems may require that the RTS 4 CTS 5 and DTR 20 lines on the modem side be tied together Application Frameworks RS 232 Communication 71 e void Drestart z0modem Restarts the modem during start of program or abnormal operation e void DzOmodem chk char buffer Checks the buffer for valid modem commands The function takes the appropriate response to the modem command if it finds a valid modem command The function returns 0 Valid modem command Invalid modem command e void 020 circ int This is an interrupt service routine for Z180 Port 0 void Ddelay 1 Creates a 1 second delay approximately If RUNKERNEL is defined suspend 50 is used t
95. urn calls the function to which ERROR EXIT points To handle such exceptions correctly make sure that ERROR EXIT contains the address of a correct exception handler Hardware Failures Hardware related failures are difficult to verify with software because the software runs on the failing hardware The only verifiable hardware failure 18 power failure Special hardware the controller detects low voltage before the power goes out completely This causes a nonmaskable interrupt NMI and the processor executes the NMI handler There is usually not much time between the NMI and complete power failure Refer to a specific controller manual for details on how best to write a power failure routine for that controller Hardware Watchdog Timer A hardware watchdog timer is a device that will reset the processor on the controller unless the timer receives a signal from the software within a specified time usually about 1 6 seconds The software must hit the watchdog timer A correctly functioning program which elects to use a watchdog timer will periodically hit the watchdog at critical places to keep the processor from resetting The assumption 1 that a failure must have occurred if the watchdog is not hit and the system will reset to allow the software to attempt a recovery 52 Failure and Recovery Dynamic C 32 v 6 x The virtual watchdog timers described Chapter 4 The Virtual Driver in this manual work by entering a
96. ver it might have been had a different time stamp And if the previous time stamp is the same as the current time stamp this Is a simple reset not a super reset A program example performing a conditional super reset is shown below CCVer is the version of the compiler Sec is the number of seconds from the beginning of 1980 main int CCVer unsigned long Sec static unsigned long CurSec if Sec CurSec super reset CurSec Sec perform super initialization 1 reset due to crash perform recovery This code only works if there is battery backed RAM that stores CurSec It could be modified to use flash EPROM or EEPROM Application Frameworks Failure and Recovery 53 Recovery of Protected Variables Z World provides a language construct and support routines for low level recovery of important variables This is particularly important if the application uses part of the battery backed RAM to store log files because the log files and the associated data structures must persist over crashes A variable may be declared to be protected When a variable or structure is protected the compiler generates the program so that when it stores a value in the variable it will 1 make a backup copy of the variable 2 set a flag indicating the backup copy 1 valid 3 change the variable and 4 reset the flag If the controller fails during the write to the variable the Z World recovery fun
97. very 1 2 second waitfor DelayMs 500 printf sd d n HCOUNT LCOUNT costate When HCOUNT gets too big reset waitfor HCOUNT gt 32000 HCOUNT 0 LCOUNT 0 In this example costatements create two execution threads within the low priority task The SRTK was designed with costatements in mind although some preemption is available Background tasks can be placed in or called from the while loop in main Background tasks will be preempted by any other task In above example the background task would consume at least 90 percent of the CPU even if it does nothing but idle because the two higher priority tasks do so little computation The Real Time Kernel A clock is required for the RTK to operate The Programmable Reload Timer PRT on the Z180 or any other device that can create periodic interrupts or ticks can be used for this purpose Generally the periodic interrupts run at a rate of 20 to 500 ticks per second Higher rates require a faster microprocessor To use the real time kernel 1 define an array of task pointers 2 specify the number of tasks and 3 define RUNKERNEL If the virtual driver is used there is no need to initialize the kernel and timer interrupts Timer interrupts will occur 40 times per second Without the virtual driver the kernel and timer interrupts must be initialized explicitly and the DelaySec DelayMs and DelayTicks functions cannot be used A
98. y five ticks and requests that Task 2 be run immediately after it completes Task 2 15 the control loop Whenever the level in the tank is low the intake flag is set opening the intake valve When the temperature 15 low the heater flag is set turning on the heater The setpoint is the desired temperature of the tank held in the variable settemp which is 56 C by default Task 4 simulates the control of a train that goes from station to station stopping for a certain time at each station The suspend function of the RTK which allows a task to suspend itself for a certain number of ticks controls the speed of the train and the time at the stations AII the graphical displays and messages generated by this task are actually output by the background task Task 5 is invoked every five ticks and calls the library routine runwatch This processes any watch lines entered while the program is running Since Tasks 0 4 have a higher priority they will not be delayed by this use of watch lines to snoop on the variables of the running program Backgnd could be called Task 6 but is named backgnd to emphasize that it runs when no other task is active All display updates are performed by this task This ensures that vital higher priority tasks are not delayed by the speed of printf Also one printf call cannot interrupt another printf since printf is not reentrant Application Frameworks Real Time Kernels 49 50 Real Time Kernels Dynamic

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