Lab 1
Contents
1. The big announcement is that the debugger works You will need to log into flounder instead of dumbo to do the lab The debugger only works on flounder Your disk files will exist on both dumbo and flounder and your account will have the same name and password on flounder as it would on dumbo Basically you can do anything but run the debugger on dumbo TO RUN THE DEBUGGER YOU MUST BE LOGGED INTO FLOUNDER Because it is rather late in the semester we will skip the assignment that was previously e mailed to you several weeks ago and proceed directly to the lab assignment discussed in class last Wednesday A copy of the lab is given below This lab will be due Monday October 14th However this may be delayed if we detect more problems with the Kern Lab computers and the debugger EEAP 282 PROGRAMMING ASSIGNMENT 1 TERMINAL INPUT OUTPUT PURPOSE This lab will introduce you to the use of branch and test instructions as well as polled input output i o You will write a program which reads the keyboard for input and then echoes it TWICE to the terminal screen LAB DESCRIPTION This lab simulates a terminal connected to a 68000 microprocessor In reality a 68000 is usually connected to a terminal or other serial device through special hardware such as a Motorola 6850 Asynchronous Communications Interface Adapter ACIA The 68000 can send and receive data through special memory locations called interface registers Because data cannot be tr2. ansferred instantaneously in the real world there are also additional interface registers which are similar to a status register and indicate whether any new data has been sent to the 68000 or whether the hardware is busy outputting data More detailed information about how the 6850 works and the function of the ACAI registers can be found on pages 474 483 of Ford and Topp This lab will use special debugger software to simulate the operation of a 6850 and its associated hardware The workstation terminal keyboard will be used for input and the db68k display will be used for output Polling refers to the fact that you must write a program with an infinite loop which monitors the 6850 registers for input from the keyboard When input is detected your software will then output the input a single character to the output using one of the special output routines provided The function of your program can be summarized by the following pseudocode loop if terminal status register 1 then character keyboard data register if character X then exit output character output character else goto loop where character is the data being input and output terminal_status_register and keyboard_data_register are the 6850 interface registers described below and output is based upon the routines described at the end of this lab description Note that the above code shows your software in an infinite loop Provision must be made i e t
3. ase characters and they must appear exactly as given above in your programs A more detailed explanation of how to use each routine is given below HexIn When it is called this routine will input a hex number from the keyboard and store its word length value in DO Example include io s _Main jsr HexIn move w DO num stores input word jat num HexOut This routine is the inverse of HexIn It will output the word in DO as a hex number followed by a line feed Example include io s _Main move w 32 D0 JSE HexOut will print 20 hex of 732 HexOutLong This routine is exactly the same as HexOut except that it prints the long word in D0 instead of only a word like HexOut does PutString This routine requires the value in AO to point to a string A string is a sequence of non zero bytes usually ASCII characters followed by a zero byte that identifies the end When it is called this routine will print to the screen the string pointed to by AO This string can have special ASCII values such as 0A for line feed or 08 for backspace Example include io s _Main lea str A0 jsxr PutString prints the below string does not add a line feed after the print str DC B TRIS is a string o0 An example of a string with special characters might be SEE DC B SOA SOA he 08 i 0A 00 This string would print two blank lines followed by he The 08 after he is a backspace so the e would be erased Then it wou
4. esting for the character X to stop your software Because not all software works the first time a short appendix to this lab describes how you can stop a UNIX process i e kill your program if it cannot be stopped otherwise For the purposes of this lab you will use two interface registers 1 terminal status register TSR at memory location 10040 READ ONLY This register shows the status of the keyboard interface In a real 6850 bit 0 is set by hardware thus you CANNOT write to this register When bit 0 1 a character is in the keyboard data register Bit 0 resets to 0 immediately after the keyboard data register is read Note that real i o takes time and bit 0 will not change immediately in your program 2 keyboard data register KDR at memory location 10042 READ ONLY This register contains the ASCII coded character input from the keyboard APPENDIX 1 HOW TO STOP A UNIX PROCESS Suppose you are in the debugger and you cannot get out of your program In addition since your program is reading the keyboard for input and commands such as CTRL D which you might type in to stop the debugger do not work To safely stop a runaway debugger you can terminate your SLIP or telnet connection However since this does NOT terminate your process you should kill all old processes when you log back in You can only kill your own processes To kill a debugger session which is still running you must be in Unix not the debugger determine
5. he debugger to simulate the operation of the 6850 ACIA as discussed above as well as to perform the functions of the various input output routines described in sections 4 3 5 and 4 3 6 of Ford and Topp The routines described in your book DO NOT WORK in the db68k debugger hence they have been replaced with the routines described in this appendix Before you can use any of these routines you must load them into the debugger along with your program This is done in two ways 1 The FIRST line of your assembly language program MUST be the following include io s which loads some special assembly language routines into your program 2 You must invoke the debugger using the command dbosk c labl com lt your program name gt The c lab1 com will cause special routines written in C to be available for use by the debugger The following files should be in your home directory iodorm com acia com extra com lab1 com io s The following routines will be available to you if you properly load the debugger with the lab1 files HexIn inputs a single hex number from the keyboard into DO W HexOut outputs the DO W in hex to the debugger screen HexOutLong outputs the DO L in hex to the debugger screen PutString outputs the string of ASCII characters whose starting address is contained in AO to the debugger screen CharOut output the character whose ASCII value is in DO B to the debugger screen Note that these names involve upper and lower c
6. ld print the i and go to the next line The end result would be two blank lines and hi on the next line Anything else printed would go on the line after hi CharOut When this routine is called it will output to the debugger screen the character whose ASCII value is in D0 Only one character will be output This character can also be a special character such as a line feed or backspace Note that these routine require that the include io s statement must be the first line of your assembly language program and you must invoke the debugger with the statement db68k c labl com lt your file name gt Several notes about this programming assignment are in order 1 The input output routines included in your assembly language program will be located at 9000 in memory You should not locate your program or any data used by your program there The file io s contains the following assembly language commands which will appear in your program listing Don t worry you are not responsible for understanding their function yet and they will not interfere with your program unless you insist on putting data or instructions at 9000 ORG 9000 HexOut MOVE W DO0 10100 RTS HexIn MOVE W 10102 10102 RES HexOut_Long MOVE L DO 10104 RTS HexIn_ Long MOVE L 10108 10108 RTS PutString MOVE L A0 1010c RTS CharOut MOVE B DO 10110 RTS 2 Many people do not know how to get a listing of the assembler out
7. put You use the L option to get the program listing to the terminal screen i e aso8k L program name If you use my aliases for doing the EEAP282 labs i e asmosk Emin lis as68k L Isg gt elas Mako ek rm i yl us desk L 0 Pex To a dds you will automatically generate a listing file with the name program_name lis 3 You can modify the file extra com to initialize the debugger pc or do other neat things The file extra com currently contains the following instructions Memory Register usp 0x3000 Memory Register ssp 0x4000 Memory Register sr 0x00 For the professional programmer you can put any startup debugger instructions you want in the file extra ccom This can be handy for initializing registers memory contents or the like For example you can automatically initialize the debugger pc to 1000 by putting the following command in the extra com file Memory Register pc 0x1000 Your lab report should conform to the following format 1 standard lab cover page with signature Use the format of the page at the end of this message Note that you must write a short several sentences at the most abstratct of what the lab was about 2 listing of your ASSEMBLED program INCLUDING symbol table 3 4 separate page answering the following questions separate page with pseudocode explanation of how program worked Questions 1 Define polling See pages 578 579 589 of Ford amp Topp 2 Is the input outpu
8. t used in this lab memory mapped or isolated input output 3 See pages 575 of Ford amp Topp Pages 577 and 578 of Ford amp Topp describe the 6850 serial interface Compare the status and input registers you used in Lab 3 with the register descriptions of the 6850 on page 578 Which 6850 registers were not used in this lab and why You will turn in the lab Monday October 14th Although the lab title page has provision for a checkout there will be no checkout of this lab at this time EEAP 282 TITLE PAGE Names Typed SIgnature No laboratory will be graded unless it is signed By signing this page you are indicating that this lab and that the work described in the lab report is your own Any complaints about grading should be directed to Prof Merat or the lab T A s TITLE Abstract Checked by
9. the process number associated with that program and issue a UNIX kill command To determine the process identification code PID of your debugger command type ps f to get something similar to the following display gt dumbo 3 ps f UID PID PAD G STIME TTY TIME COMMAND merat 23604 23602 5 14 05 13 ttyu0 0 00 ps f merat 23534 23533 0 14 04 03 ttyu0 0 02 csh csh merat 23602 23601 0 14 05 06 ttyu0 0 00 bin esh i merat 23601 23534 0 14 04 42 ttyu0 0 00 db68k examl The display shows the user in this case merat followed by the PID number you want However because UNIX is multi tasking you can have many processes running simultaneously You should examine the right hand column looking for a command which begins with db68k The PID shown in this row is the one associated with your runaway debugger program In this example the correct number is 23601 To stop the process type dumbo 4 kill 23601 This will typically result in a message like the following dumbo 5 Stopped tty output dumbo 7 Reset tty pgrp from 23534 to 23602 Closed which indicates that the process has been killed and you can get back to what you were doing Note that kill is a priviledged UNIX instruction and you can only kill your processes YOU CANNOT ASK ANYONE ELSE TO KILL YOUR PROCESSES FOR YOU However Wes can kill anyone s processes APPENDIX 2 Emulation Code User s Manual Special input output routines have been written for t
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