PLC↔CAN interface
Contents
1. A protocol has been agreed upon for transfer of data and commands via the RS232 connec tion between the application running on the SPICAN module PLC CAN and the PLC appli cation see APPENDIX C Protocol on the PLC CAN lt gt PLC for a description The PLC CAN appli cation maps messages to and from the PLC application onto appropriate CAN messages This document provides a detailed description of the interface to the PLC seen from the CAN bus side The protocol used on the MVD CAN network is CANopen 1 This document assumes that the user has at least a basic knowledge of this protocol ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 2 Operation The MVD Controls Supervisor should be able to monitor the status of the MVD cooling sys tem to set a number of warning and error limits in the system and be able to assert general control over the PLC such as start stop reinitialise All communication will take place using CAN bus communication i e the CANopen protocol a standardized application layer protocol for CAN bus 1 All relevant PLC parameters are mapped by PLC CAN to an object in the CANopen Object Dictionary OD in the Manufacturer Specific Profile Area shown in Table 3 By making the parameters accessible for reading and writing through the CANopen SDO Service Data Object mechanism and mapping appropriate parameters to CANopen PDOs Process Data Objects a straightforward and CANopen compliant interface2. 21 P1 warning level minimum RW 22 P1 warning level maximum 16 RW 23 P1 error level maximum U16 RW 24 P2 error level minimum 25 P2 warning level minimum P2 warning level maximum 27 P2 error level maximum Doo S O ee continued in the next table Table 3 Manufacturer specific Profile Area of the CANopen Object Dictionary for the PLC CAN device mapped into PDO1 see sect 2 2 mapped into PDO1 see sect 2 2 TH E a HE O H LR I et ITE L E Eo ao pene eat L TH IE L LI HTH E E ae L a ee E oe L HET LL L L L E I 7 Oo T 15 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Manufacturer specific Profile Area PLC CAN continued Index Name Data Attr Default Comment hex Object 2000 o o continvied from previous table H1 warning level minimum H1 warning level maximum Hi error level maximum H3 error level minimum H3 warning level minimum p H3 warning level maximum H3 error level maximum w AF warning level minimum AF warning level maximum AF error level maximum U16 Interlock delay in seconds 0 200 Error input override see section 2 2 AP1 error level maximum AP2 error level maximum H2 error level minimum H2 warning level minimum H2 warning level maximum H2 error level maximum Max PLC monitoring subindex Determines up to which subindex for PDO2 of Object 2000 is to be monitored using PDO2 RTR and or SYNC Access to other sub
3. set or reset individual bits in the Global Status PLC parameter if their function is defined see section 2 1 SDO messages to as well as from PLC CAN always contain 8 databytes and the mecha nism to transfer data is SDO expedited transfer meaning that the data is contained in the message and is 4 bytes or less in size A segmented transfer would be necessary if the data to be transferred contained more than 4 bytes If for some reason a node cannot service an SDO it will respond with an SDO Abort Domain Transfer message see example in section 2 7 2 6 Setting PLC Error and Warning Limits The PLC error and warning limits can be read and written by accessing the appropriate subindices 16 to 47 see Table 3 of OD index 0x2000 using the CANopen SDO mechanism The values read and written are in ADC counts If physical values are required a conversion from or to physical values has to be done by the user or the host application To set for example P2 warning level minimum subindex 25 0x19 hexadecimal to a value of 10000 0x2710 hexadecimal the following CAN message SDO expedited transfer is to be sent Host PLC CAN Byte COB ID fe Se H ee HE 0x600 0x2B 0x00 0x20 0x19 0x10 0x27 Node_ID If successful PLC CAN will reply with the following CAN message PLC CAN Host Byte E L H T 2 a fs aaa at THT 0x580 0x60 0x00 0x20 0x19 Node_ID To read for example T error level maximum subindex 19 0x13
4. hexadecimal the follow ing CAN message is to be sent Host gt PLC CAN Byte COB ID eee ere ET ee ee eS T 0x600 0x40 0x00 0x20 0x13 Node_ID The reply CAN message SDO expedited transfer of PLC CAN looks for example like this ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 PLCCAN Host FS Fa Sa ee a a 0x580 an 0x20 0x13 0x34 TE Node_ID In this case it means that the T error level maximum shown in bytes 4 and 5 is equal to 0x 1234 4660 decimal SDO messages to as well as from PLC CAN always contain 8 databytes and the mecha nism to transfer data is SDO expedited transfer meaning that the data is contained in the message and is 4 bytes or less in size A segmented transfer would be necessary if the data to be transferred contains more than 4 bytes If for some reason a node cannot service an SDO it will respond with an SDO Abort Domain Transfer message see example in section 2 7 2 7 Storing PLC CAN Parameters Some parameters can be stored permanently onboard the PLC CAN node in non volatile memory an EEPROM by writing the string save to OD index 0x1010 The CANopen SDO mechanism is used to accomplish this Host PLC CAN Byte COB ID e e gp pe ED Secs ae ea A Se fe ra 0x600 0x23 0x10 0x10 o o 0x76 0x65 Node_ID v Ce with OD index 0x1010 in byte 1 2 and subindex 1 in byte 3 The parameters stored are OD index 0x1800 subindex 2 PDO commu
5. to the cooling system PLC has been created One of the PLC CAN s features is that it can autonomously monitor the PLC for status changes which if they occur result in a CAN message 2 1 Initialisation After power up watchdog reset manual reset or CANopen initiated reset actions the PLC CAN node sends a so called Bootup message defined by the CANopen standard as soon as it has finished its initialization this is a CAN message with the following syntax PLC CAN NMT Slave Host NMT Master COB ID Byte 0 0x700 Node ID 10 In case of a watchdog or manual reset the Bootup message is followed by a CANopen Emer gency message as listed in the table in section 2 8 22 PLC Parameter Block The PLC parameters accessible via the CAN bus are listed under Object Dictionary object 0x2000 in Table 3 The descriptions of the parameters in this table speak for itself for most of the parameters listed Some of the parameters are read only others are read write Some of the parameters require a more detailed description and or subdivision into bits which is provided in the tables below ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 PLC Digital Inputs OD index 0x2000 subindex 7 in error free situations all used bits are 1 unused bits are 0 s all bits are read only Description when bit 1 0 Coolant flow OKAY Pump temperature OKAY PLC Error Input Override Setting OD index 0x2000 subindex 41 when set to 1 t
6. 01 1 2 Transmit PDO yanappine Reed py Data type PDOMapping 0 Number ofentries Us EE Multiplexor see DSP 404 Size 8 bits bad ee he ed 2000FD10 OD index 2000 sub index 253 PLC parameter via a mukiplexor Size 16 bits Table 2 Communication Profile Area of the CANopen Object Dictionary continued The Manufacturer Status Register Object Dictionary index 0x1002 a 32 bit object pro viding more specific status information about the PLC CAN module i e the type of errors that have occurred reported by Emergency Objects The layout of this Register is as follows bit3 bit2 biti bito not L PLC status IAAT PLC CAN PLC CAN communication unexpected operation EEPROM read EEPROM write timeout parameter index aborted RS232 CRC error error RS232 received RS232 14 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Manufacturer specific Profile Area PLC CAN hex Index Object dec 2000 PLCparameterblock Aray o y O 0 Numberofentries U16 RO 553 gt S O 1 Temperature D Uo RO 2 Pressure PUT V6 ROP 3 6 RO o O 4 RO ey 5 RO Doo RO Doo y O 7 RO RO Doo y O l Error status Ul6_ RW i 11 Global status U16 RW i 12 reserved O 13 RO 14 RO 16 T1 error level minimum RW 17 T1 warning level minimum RW 18 T1 warning level maximum RW 19 T1 error level maximum RW 20 P1 error level minimum RW
7. Error Code Object 0x1001 The following Emergency messages are defined for PLC CAN Bevan Emergency Error Register Error Code bit Object 1001H byte 0 1 byte 2 Watchdog or 0x6000 0x01 Byte 3 4 5 6 Manufacturer Device Name manual front Object Dictionary index 0x 1008 panel reset Byte 7 0 CAN controller 0x8100 0x10 Byte 3 1 overrun mes Byte 4 counter modulo 256 sage lost Byte 5 CANSTA CAN controller status register Byte 6 7 0 CAN controller 0x8100 0x10 Byte 3 2 error Byte 4 counter modulo 256 communication Byte 5 CANSTA CAN controller status register error Byte 6 7 0 Local CAN 0x8 100 0x10 Byte 3 3 message buffer Byte 4 counter modulo 256 overflow Byte 5 CANSTA CAN controller status register message lost Byte 6 7 0 Manufacturer specific Error Field Description byte 3 7 me communication Byte 4 parameter index for which timeout occurred time out Byte 5 number of received chars in RS232 buffer Byte 6 7 0 i unexpected Byte 4 parameter index expected parameter index Byte 5 parameter index received Byte 6 7 0 RS232 OxFFOO 0x80 Byte 3 0x10 PLC poll opera Byte 4 poll error counter tion aborted Byte 5 6 7 0 EEPROM 0x5000 0x80 Byte 3 4 aema O a CRC error Byte 4 5 6 7 0 Note that the Error Register Object Dictionary index 0x1001 can have one or more of the bits shown above set depending on the node s history of error occurrences The table sh
8. ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 PLC lt OCAN interface for the ZEUS Micro Vertex Detector MVD Cooling System Henk Boterenbrood NIKHEF Amsterdam February 2000 USER DOCUMENTATION Version 1 4 ABSTRACT This document describes the CANopen interface to the CAN module that provides an inter face to the PLC that controls the ZEUS Microvertex Detector MVD cooling system The SPICAN CAN module equipped with this application firmware is referred to as PLC CAN in this note Contents 1 INTRODUCTION viscissssacisatessesiscscacetatessecsccosscssateccesiachsscesseaddesbecedacssalesdesesdasasssscassoasecasncess 2 2 OPERATION EERE E E A EE E E E E 3 Z ENAS AT ON R a a a fe dake enelisea taniee es lok con dlaveet 3 E PEC PARAMETER BLOCK aouo E a A A 3 2 3 MONITORING PLC ERROR WARNING AND GLOBAL STATUSRS 6 2 4 MONITORING PLC PARAMETERS cccccccccccccssssssceccccccssessessesccccssssusesesesccesssssuueeseeecesseeees 7 2 5 SETTING PLC ERROR WARNING AND GLOBAL STATUSES cccccsssessssccccceseeseessseccesseees 8 2 6 SETTING PLC ERROR AND WARNING LIMITS snsssneessseensssoenssseesssscenrssceressersessceresseersse 9 2 7 STORING PLC CAN PARAMETERS ccccccccccccssssssscecccccecesssssscscccccessssessescecceseseueneusesses 10 2 8 EMERGENCY OBJECTS cccccccccccccccsssssssccccccccessssssesccsccessessssesccsccssssuusssescesessesuseusesscsses 12 3 OBJECT DICTIONAR Vosiicccssisssccssscccoscsssaseseccossosscsscacaccsossoscc
9. e message the error counter is reset to zero 19 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Bytel E f Bytel bit 6 0 Byte 2 3 preferred CANopen PLC parameter Attr as parameter id parameter data access mechanism Temperature ro 0 Pressure 1 P1 Ro 0 0x02 Pressure 2 P2 mo o oo Hygrometer 10D ro 0 om Myom 30 Ro_ 0 oo Arowa rof o o Ditampi Ro o o Hygrometer 203 R0 o0 o Error Saws r 0o 0x09 Warning Stas R o CON 0 TE E s E 6 Ox0A reserved boe o ee ees Tmn amar R o oo 5 Oxi E 0x13 eee Plmin error sd min error Seton 0x14 0x15 0x16 OxI7 D TE GEE E e Loree Green Ce HE x19 C mo OxIA xB az eal G TID OxIE TIP S T2 0x21 022 023 E 21 SDO 5 o H in C E ee AF min error 0535 AF max warning 0x26 fF ih G w l S eed eae n S lt 20 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Bytel PLC parameter Attr bit7 R W W HI HE E GEE R delay _RW_ _07T_ o HS Error Input Override RW O T 0x20 E H R G OE REG EEE C H RW on oan H HS A L T Se HE E E delta P2max error T RW O T B f DE ee E E e N Tamme w on o 1 HS H2 min warning Rw on o _ 2 max warning rw on ow o H2 max error Rw on Bytel bit 6 0 Byte 2 3 CANopen parameter id parameter data access mechanism Table 5 List of messages exchan
10. ent 1 server SDO 1010 __ Store parameters Array Save stuff in onboard EEPROM Poa Highest index supported L 0 ROC de 1 Save all parameters U32 RW 1 read 1 write save store all 1011 Restore default parameters Array Invalidate stuff in onboard EEPROM TEE Highest index supported US RO 1 Restore all parameters U32 RW 1 read 1 write load invalidate all stored Table 1 Communication Profile Area of the CANopen Object Dictionary 13 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Communication Profile Area PLC CAN continued hex Index Object hex ters a ia Number of entries 8 RO 2 1 COB ID used by PDO TE SOE to CANopen Prede Node ID fined Connection Set 2 Transmission type U8 RW FE 254 manufctr specific get PLC statuswords at RTR default 1 get PLC statuswords at SYNC 1801 i 2 Transmit PDO parame feu Ee N Data type PDOCommPar ters PPT tines roo Pons PROP ai ID used by PDO S Lh to CANopen Prede Node ID__ fined Connection Set Ea kaa type RW 254 manufctr specific get PLC FOE at RTR default get PLC data at SYNC 1A00 T I Transmit PDO mapping Record Data type PDOMapping 02 Numberofentries 8 2 ROS 3 a ee a e an ae reel Status Size 16 bits Cooling System Warning 20000A 10 OD index 2000 sub index 10 R san aT Cooling System Global 20000B10 OD index 2000 sub index 11 IE sees Pe pe Meee G ere 1A
11. er every socalled Remote Transmission Request RTR for PDO2 the node sends 8 PDO messages one message for every PLC parameter configured for monitoring The CAN Remote Frame that constitutes the RTR has no data bytes and looks like this Host gt PLC CAN COB ID 0x280 Node_ID Note that an RTR is sent to and received by only one particular node The PDO2 transmission type can also be saved to the PLC CAN on board non volatile memory if required see section 2 7 2 5 Setting PLC Error Warning and Global Statuses The PLC parameters Error Status Warning Status and Global Status can be written to using the CANopen SDO mechanism Error Status and Warning Status can be reset to zero by writing 0 to the corresponding OD objects To reset for example the Error Status word the following CAN message SDO expe dited transfer is to be sent Host PLC CAN Byte COB ID oo aoe a a a S 2 ae T ee Se Node_ID If successful PLC CAN will reply with the following CAN message PLC CAN Host cos ip Byte T L T H HT TH T I te THI 0x580 0x60 0x00 0x20 0x09 Node_ID ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 Note that in case several errors are present multiple resets of the Error Status by writing zero to the OD object are needed until the error status is cleared and the cooling system can be started A similar command reply message pair can be used to reset the Warning Status word or to
12. eter is set in units of 100 ms if set to 1 PLC CAN polls the PLC with a frequency of 10 Hz when set to 2 with a frequency of 5 Hz when set to 10 with a frequency of 1 Hz etc etc up to a maximum period of 25 5 seconds When OD index 0x2002 is set to 0 PLC CAN does not poll the PLC statuswords and the host should periodically issue an RTR for PDO1 as described above if it wants to stay up to date on the PLC statuswords Polling and thus sending of event triggered PDO1s only takes place when PLC CAN is in Operational state PLC CAN state is controlled by CANopen NMT messages See APPENDIX C Protocol on the PLC CAN lt gt 5PLC RS232 connection for more details on PLC polling and the communication between PLC CAN and PLC 2 4 Monitoring PLC Parameters PDO2 messages are used to transfer other PLC data that is to be monitored on a regular ba sis The data to be monitored are16 bit data and are numbered according to the subindices of PLC CAN Object Dictionary index 0x2000 Table 3 One PDO2 CAN message is used to transfer one 16 bit PLC parameter preceeded by its Object Dictionary subindex Thus every monitoring request results in a series of PDO2 messages one PDO2 for every PLC parameter to be monitored The number of parameters listed at OD index 0x2000 to be monitored starting from subin dex 1 can if required be set to any value by writing to OD index 0x2001 using the CANo pen SDO mechanism This parameter has a defau
13. ged over RS232 between PLC CAN and the PLC RO Read Only RW Read Write 0 don t care LSB Least Significant Byte MSB Most Significant Byte RTR triggered by CAN Remote Transmission Request SYNC triggered by CANopen SYNC message CoS triggered by Change of State 21
14. he corresponding error input is ignored by the PLC application all used bits are read write unused bits are 0 o Coolant flow SS PLC Error Status OD index 0x2000 subindex 9 only one error bit bits 2 15 is set at a time in case several errors occurred repeated resets of the PLC Error Status by writing zero to the OD object are needed until the error status is cleared Error bit bit 0 goes to 0 the cooling system can only be started when the Error bit bit 0 is 0 the interlock bit bit 1 is set to O only after the cooling system is started 0 Error OR of errors presentin PLC RO 1 Interlock RO 6 Humidity sensor H3 W 8 Pressure sensor P2 W 9 Airflow AF RW 14 Notused P 15 Notused ROT ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 PLC Warning Status OD index 0x2000 subindex 10 Description o Warning COR of bits 11015 6 TAaimowan Ce Noru Co Nouse PLC Global Status OD index 0x2000 subindex 11 When both bits 0 and 1 of this word are written as 1 the PLC switches to a so called de ventilation mode where the cooling system pump is running with all valves closed in or der to expel any remaining air from the cooling liquid in the system Description 0 Cooling system ON 1 or OFF 0 Deventilate when system ON bit 0 PLC Interlock Delay OD index 0x2000 subindex 40 The interlock delay is t
15. he time in seconds between the occurrence of an error condition in the cooling system and the moment the hardware interlock intervenes and systems get switched off or get taken into a safe state this time allows other MVD control systems to shut down gracefully or take appropriate actions before the interlock is activated or even to prevent subsequent activation of the interlock ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 2 3 Monitoring PLC Error Warning and Global Statuses Before PLC status and data monitoring can start the PLC CAN node has to be set into Op erational state using the following 2 databyte CANopen NMT message Host NMT Master gt PLC CAN NMT Slave COB ID Byte 0 Byte 1 0x000 1 lt Node ID gt or 0 Start_Remote_Node all nodes in network There is no reply to this message PLC data that is subjected to regular monitoring can be read out using the CANopen PDO mechanism A PDO nessage is a non confirmed CAN message with one sender and one or more receivers containing no protocol overhead only data 1 to 8 bytes It is assumed that receivers of a PDO message know the meaning of the data content of a PDO message PLC CAN can produce 2 different PDOs which we will call here PDO1 and PDO2 PDO2 messages are described in the next section The PLC parameters Error Status Warning Status and Global Status are found in the PLC parameter block in the Object Dictionary index 0x2000 subindices 9 10 a
16. ication with PLC SPICAN component side backplane connector space for DC DC convertor space for fuse Micro key 20CN592 microcontroller module NB wire bridges in place as shown in case of local power supply J1 80C592 internal watchdog J1 1 2 closed disabled J1 2 3 closed enabled J3 powerfail interrupt request via P1 0 INT2 pin open interrupt disabled J4 external watchdog enable selector 80C592 pin P1 1 to MAX691 open watchdog dis abled J5 reset jumper closed system will reset 17 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 J6 J7 serial port signal connection disconnection SPICAN solder side Power options Local power supply via backplane J8 J9 closed J10 J11 open DC DC convertor and fuse NOT placed wire bridges in place Ext 5 V power supply via CAN connector J8 J9 open J10 J11 closed DC DC convertor NOT placed wire bridges in place fuse placed Ext 9 36V power s via CAN connector J8 J9 open J10 J11 closed DC DC convertor and fuse placed Additional power option Battery backup J13 open APPENDIX B Connector Layout 9 pin D sub male CAN connector Pin Signal o COEN a 0 e 6 Ee 83l 9 ve 18 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 APPENDIX C Protocol on the PLC CAN gt PLC RS232 connection The cooling system s PLC works autonomously and independently but can be controlled and moni
17. indices using PDOlor SDO PLC status polling period Time between consecutive polls for PDO1 by PLC CAN of PLC error and warning status in units of 100 ms 0 means polling not enabled AF error level minimum sf 29 30 31 32 33 35 37 38 39 41 42 43 45 47 Table 4 Manufacturer specific Profile Area of the CANopen Object Dictionary for the PLC CAN device continued References 1 H Boterenbrood CANopen high level protocol for CAN bus Version 3 0 NIKHEF Amsterdam March 20 2000 http www nikhef nl pub departments ct po doc CANopen30 pdf 16 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 APPENDIX A LEDs Switches and Jumpers SPICAN Frontpanel Red LED CAN controller error bus errors buffer overflow SPICAN Green LEDs CAN and SYS 4 5V power supply indications for CAN bus driver and onboard electronics resp message s lost Green LED Red LED CAN bus activity error occurred in RS232 communication with receiv ing sending PLC check for received Emergency Objects and or Manufacturer Status Register Node ID and CAN baudrate setting 0x01 0x7F Node ID 1 to 127 125 kbit s 0x81 OxFF Node ID 1 to 127 250 kbit s top switch high nibble bottom switch low nibble Green LED T O activity i e RS232 communication with PLC in progress Reset button CAN bus connector S232 connector 4800 baud 8 N 1 for code downloads 9600 baud 8 N 1 for commun
18. lt value of 6 but could be increased to e g 15 if additional PLC parameters are added to OD index 0x2000 at subindices 12 to 15 marked reserved See Table 3 A change to parameter 0x2001 can be made permanent by saving it to the PLC CAN on board non volatile memory see OD index 0x1010 in Table 1 A PLC CAN PDO2 CAN message has 3 data bytes PLC CAN Host COB ID Byte 0 Byte 1 2 0x280 PLC Parameter Index 16 bit PLC Parameter Node_ID with PLC Parameter Index runs from 1 to 8 or to whatever value has been set in OD index 0x2001 PLC Parameter 16 bits value LSB in byte 1 MSB in byte 2 The definition of the data content of PDO2 its mapping can be found in the Object Dic tionary at index 0x1A01 A monitoring request as mentioned above is either a SYNC message or an RTR Remote Transmission Request for PDO2 Whether PLC CAN responds to either one depends on the configuration of its PDO2 transmission type OD index 0x1801 subindex 2 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 e PDO2 transmission type 1 after every socalled SYNC message issued on the CAN bus PLC CAN sends 6 or PDO2 messages one message for every PLC parameter configured for monitoring The SYNC message is a CAN message with a fixed COB ID and no data bytes Host all SYNC slave nodes COB ID 0x080 Note that all nodes configured to respond to a SYNC will react to a SYNC message e PDO2 transmission type 254 aft
19. nd 11 They can be included in the regular monitoring scan of the PLC parameters as described in the next section However to enable a more frequent check or PLC CAN autonomous check see below on the PLC status words alone an extra PDO has been defined that contains only these status words 6 bytes in total PDO1 The definition of the data content of PDO1 its mapping can be found in the Object Dic tionary at index 0x1 A00 A PLC CAN PDO1 CAN message has 6 data bytes PLC CAN Host Byte COB ID coap PS a a 0x180 Error Error Warning Warning Global Global Node_ID Status Status Status Status Status Status LSB MSB LSB MSB LSB MSB This PDO1 message can be requested by the host by sending a socalled Remote Transmis sion Request RTR for PDO1 The CAN Remote Frame that constitutes the RTR has no data bytes and looks like this Host gt PLC CAN COB ID 0x180 Node_ID Typically the PLC CAN status words would be read out every second for example and the PLC parameters from the previous section only every 30 seconds or so ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 However the preferred way is to set the PDO1 object to event triggered meaning that as soon as PLC CAN detects that one or more bits in the statuswords have changed it will send a PDO message To achieve this PLC CAN polls the PLC periodically for its status words with a period that can be set in OD index 0x2002 This param
20. nication parameters OD index 0x1801 subindex 2 PDO2 communication parameters OD index 0x2001 number of PLC parameters to be monitored OD index 0x2002 PLC status polling period PLC error and warning limit settings are assumed to be stored by the PLC on the PLC If the store operation succeeded the controller sends the following reply PLC CAN Host Byte COB ID cop ts S L Node_ID 10 ZEUS MVD PLC CAN interface vl 4 19 Feb 2001 If the store operation did NOT succeed the controller sends the following reply SDO Abort Domain Transfer error reason hardware fault for details see 1 PLC CAN Host Byte Pl ee ee Re eS a 0x580 0x80 0x10 0x10 1 6 6 Node_ID Error Code Error Class Parameters can be reset to their default values by invalidating the corresponding contents of the EEPROM by writing to OD index 0x1011 using this time the string load in bytes 4 to 7 of the SDO message Note that the default values take effect only after a subsequent reset of the node Default values are listed in the Object Dictionary tables 11 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 2 8 Emergency Objects Emergency messages are triggered by the occurrence of an internal fatal error situation An emergency CAN message has the following general syntax PLC CAN Host COB ID Byte 0 1 Byte 2 Byte 3 7 0x080 Emergency Error Register Manufacturer specific error field Node_ID
21. ows the Error Register bit that gets additionally set when described error occurs 12 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 3 Object Dictionary Table 1 to Table 4 show in detail the Object Dictionary OD of the PLC CAN CANopen application Column Attr shows the access rights attribute of an object RO read only RW read or write WO write only All entries in the OD are accessed using the CANopen SDO mechanism with expedited transfer object data content always lt 4 bytes Communication Profile Area PLC CAN Index Sub Name Data Attr Default Comment hex Index Object hex 1000 Devicetype U32 RO 00000000 _ 1001 Error register U8 Error bits according to DS 301 error status overview 1002 Manufacturer status reg T U32 RO 0 seebelow 1004 __ PDOs supported Array i ee 0 Total PDOs supported U32__ RO__ 00000002 0 receive 2 transmit PDO 1 PDOs syne U32__ RO 00000002 PDO after SYNC 2 PDOsasync U32 RO 00000002 PDO after RTR or event 1008 _ Manufacturer device name _ VisStr_ RO _ SPIC SPICAN module 100A Manufacturer software VisStr PC10 MVD Cooling System version PLC to CAN Version 1 0 100B Node identifier U32 RO set by frontpanel hex switches 100E Node Guarding COB ID U32 0x700 According to CANopen Prede Node ID_ fined Connection Set 100F SDOs supported U32 RO 00000001 Ocli
22. s in this case it is the responsibility of the CAN host application to check that the subindex of the ob ject which equals the parameter identifier in the SDO reply matches the one in the corre sponding SDO request Bytes 2 and 3 of the PLC CAN command message either have a don t care value PLC CAN requests a read access or contain the parameter value 16 bit LSB first to be writ ten set in the PLC Bytes 2 and 3 of the PLC reply message contains the current or newly written value of the parameter When a time out occurs on reception of the reply from the PLC in response to a message from the PLC CAN application an appropriate CANopen EMERGENCY message is sent again see section 2 8 and PLC CAN reinitializes its RS232 interface and buffers The time out is set to 100 ms If a time out or parameter index mismatch occurs during the automatic PLC status scanning operation of the PLC CAN application the appropriate CANopen EMERGENCY is sent The scanning operation is not suspended until a total of 50 such errors in a row occur currently hardcoded A successful PLC status scan decrements the error counter by one This is to prevent a possible endless stream of error message when the connection to the PLC is perma nently lost The aborting of further PLC status scanning is notified to the user by a separate CANopen EMERGENCY again see section 2 8 The scanning operation can be resumed by sending a CANopen NMT Start Remote Nod
23. ssososdcsescoascdsdacescsecsoassdsoasses 13 REFERENCES issscescccatsesssecssesccscsacoceccdeacocadsecsSecescsccsessecssecesescesadsccssescncodesedsacssoccseasesedsossdoasseads 16 APPENDIX A LEDS SWITCHES AND JUMPERS u 0 ccssssscsssssscccsssssccsssssccsccssscees 17 APPENDIX B CONNECTOR LAYOUT sss sss sss sss assa assa sassa aana anana ananas 18 APPENDIX C PROTOCOL ON THE PLC CAN amp PLC RS232 CONNECTION 19 ZEUS MVD PLC CAN interface v1 4 19 Feb 2001 1 Introduction The CAN fieldbus network that interconnects a number of the MVD control systems and the MVD Controls Supervisor is used by the Supervisor to monitor and control the various MVD subsystems One of the subsystems connected to the CAN network is the PLC controlled cooling system of the MVD frontend electronics The PLC SIEMENS S7 of the MVD cooling system does not have an interface to connect it directly to a CAN bus But it does have an RS232 interface which is used to connect it to a so called SPICAN module which features an RS232 interface as well as a CAN interface The SPICAN module can thus provides an interface between the PLC and the CAN network as illustrated below in Figure 1 Custom application firmware has been developed for the SPI CAN module to provide a communication interface between RS232 and CAN bus digital and analog I O SIEMENS S7 PLC CAN SPICAN module CAN bus Figure 1 Interface of MVD Cooling System to CAN bus
24. tored via its interface to the CAN bus formed by the PLC CAN module and an RS232 connection between the PLC and the PLC CAN The RS232 connection is set to 9600 baud 8 bits 1 stop bit no parity The protocol over the RS232 connection between the PLC CAN module and the PLC is a simple command reply type of protocol where the PLC CAN module is the initiator of the command message the PLC only generates a message in reply to a message from the PLC CAN The full list of messages is shown in Table 5 together with the preferred CANopen ac cess mechanism for each individual parameter for more details of this see the tables contain ing the PLC CAN Object Dictionary and the description of the PDOs The command message as well as the reply message consists of 3 bytes The first byte con tains a parameter identifier in bit 0 to 6 bit 7 is 1 when the PLC CAN requests a write access to the parameter and bit 7 is O when a read access is requested the value of byte 0 of the reply must be identical in the reply from the PLC This is checked by the PLC CAN application for data that is subsequently put in a CANopen PDO message before being put in the PDO the parameter identifier is removed When the PLC CAN application detects such a mismatch in the parameter identifier in the RS232 command and reply message an appropriate CANopen EMERGENCY message is sent see section 2 8 The parameter identifier is not checked for CANopen SDO access of PLC parameter
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