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Does anyone have any sample code to transmit and receive messages through the CAN port for the DP256 model of HC12? Please let me know... i tried to program it, but it ended up that i was using the wrong version... and the registers were all in a different place, and confusion ensued... please let me know ASAP guys. Thanks. |
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CAN Programming
Started by ●January 20, 2004
Reply by ●January 20, 20042004-01-20
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From Oliver Thamm's site some time ago http://hc12web.de/ coutesy of Andreas Dannenberg Name: CAN_A4.A ; Ver.: 1.0 ; Func: CAN-Bus demo for HC12compact-Board (C)MCT Lange & Thamm ; receives data from the SC0 (serial interface) of the HC12, ; sends them out via the CAN-Bus and vice versa ; Auth: Andreas Dannenberg, eMail: ; Student of electrical engineering/telecommunications at ; Leipzig University of Applied Sciences (HTWK) ; Date: Sept 28 1999 ; Rem.: Translate with "A12 CAN_A4" ;============================================================================= ; Chip-Select addresses of the CAN-Controller on the HC12compact-board CAN_ADDR equ $0301 ; select CAN-controller register CAN_DATA equ $0201 ; access to CAN-controller register ; Registers of SJA1000 in BasicCAN-mode CR equ 0 ; Control Register CMR equ 1 ; Command Register SR equ 2 ; Status Register ACR equ 4 ; Acceptance Code Register AMR equ 5 ; Acceptance Mask Register BTR0 equ 6 ; Bus Timing Register 0 BTR1 equ 7 ; Bus Timing Register 1 OCR equ 8 ; Output Control Register TXBUF equ 10 ; Transmit Buffer RXBUF equ 20 ; Receive Buffer CDR equ 31 ; Clock Divider Register cpu 68hc12 ; pseudo instructions to padding off ; build HC12-code include "reghc12.inc" ; include HC12-standard registers org $0800 ; program runs in RAM ; ***** CAN controller SJA1000 init ***** ; ; physical layer interface: PCA82C250 transceiver from Philips Semiconductors ; connected to pins RX0 and TX0 of the CAN controller ; (pins 45 and 47 of ST4 of the HC12compact board) ; ; Bus timing values for a bit rate of 100 kbit/s, oscillator frequency is 16 MHz: ; Pay attention while selecting Time-Segment values to meet the CAN-Standard! ; (refer to SJA1000-Datasheet for more detailed information about CAN-timing) ; ; baudrate prescaler: 5 -> tSCL = 2 * 1/16 MHz * (4+1) = 625 ns (CAN System Clock Period) ; sync segment: tSYNCSEG = 1 * tSCL ; time segment 1: 11 -> tSEG1 = tSCL * (10+1) = 6.875 us ; time segment 2: 4 -> tSEG2 = tSCL * (3+1) = 2.5 us ; ; bit time: tBIT = tSYNCSEG + tSEG1 + tSEG2 = 10 us ; bit rate: fBIT = 1 / tBIT = 100 kbit/s ; ; The CAN-Bus address of the SJA1000-controller will be set to %10000000000 ; (11 bits, CAN2.0A). ; Rem.: In BasicCAN-Mode, the SJA1000 only has 8-bit wide acceptance mask ; and code registers. That's why the last three bits of the identifiers of incoming ; messages are ignored and all messages beginning with %10000000 will be received. Start ldx #CR ; enter Reset-Mode in order to configure the ldaa #$01 ; SJA1000 CAN parameters jsr writeSJA1000 ; write to CAN-Controller register ldx #CDR ; bypass input comperator, BasicCAN mode ldaa #$48 ; external clock output off jsr writeSJA1000 ldx #OCR ; set output control register for using CAN- ldaa #%00011010 ; transceiver: normal Mode, TX0 push pull, TX1 float jsr writeSJA1000 ldx #BTR0 ldaa #%00000100 ; baudrate prescaler 5, synchron jump width 1 jsr writeSJA1000 ldx #BTR1 ldaa #%00111010 ; 1 samplepoint, tSEG2: 4 cycles, tSEG1: 11 cycles bsr writeSJA1000 ldx #AMR ldaa #$00 ; don't mask identifiers of received messages jsr writeSJA1000 ldx #ACR ; accept only messages with identifier ldaa #$80 ; starting %1000 0000 (other 3 bits don't care) jsr writeSJA1000 ldx #CR ; leave reset-mode, disable CAN-interrupts ldaa #$00 ; and switch to normal operation jsr writeSJA1000 ; ***** Prepare the transmit buffer to send out a byte ***** ; ; Transmit buffer layout (in BasicCAN-Mode): ; (the RXBUF receive buffer layout is similar) ; ; TXBUF : Identifier Byte 1 (ID.10 .. ID.3) ; TXBUF+1 : Identifier Byte 2 (ID.2 .. ID.0, RTR, DLC.3 .. DLC.0) ; TXBUF+2..9 : Transmit Data Bytes 1..8 ; ; ID.10 .. ID.0 : Identifier bits of the message ; RTR : Remote Transmission Request (1=request transmission, 0a frame) ; DLC.3 .. DLC.0 : Data Length Code (0 to 8) ldx #TXBUF ; Set up Identifier Byte 1 ldaa #$81 ; send data to CAN-adress %1000 0001 bsr writeSJA1000 ldx #TXBUF+1 ; Set up Identifier Byte 2 ldaa #$01 ; the rest of 11-bit identifier: %000 bsr writeSJA1000 ; and 1 byte to send (DLC.3 .. DLC.0) bsr initSC0 ; Set up the Serial Interface 0 ; ***** Main program loop ***** ; ; Checks if new serial data is avaiable and transfers them via CAN-bus ; with the identifier %10010000000 and ; redirect messages from the CAN-Bus with identifiers starting with ; %10000000 to the host PC. ; The programm can be terminated by sending a 27 (ASCII-ESC) to the ; serial interface of the HC12compact board. Send brclr SC0SR1,$20,Rec ; if SC0 receive buffer=empty, check for CAN data bsr getSC0 ; fetch new data from SC0 cmpa #27 ; <ESC>-key pressed? beq End ; yes -> terminate program bsr putSC0 ; local echo of serial data psha ; save byte onto Stack Sloop ldx #SR ; read out SJA1000 Status Register bsr readSJA1000 anda #%00000100 ; mask the Transmit Buffer Status Bit (TBS) beq Sloop ; wait until the Transmit Buffer is released pula ; get byte back from Stack ldx #TXBUF+2 ; write new data into the CAN- bsr writeSJA1000 ; transmitt buffer ldx #CMR ; set transmission request bit ldaa #$01 ; (transmit data via CAN) bsr writeSJA1000 Rec ldx #SR ; read out the SJA1000 status register bsr readSJA1000 anda #%00000001 ; isolate receive buffer status bit beq Send ; if CAN receive buffer=empty, check for serial data ldx #RXBUF+2 ; read new byte from receive buffer bsr readSJA1000 bsr putSC0 ; transmit the byte to host PC ldx #CMR ldaa #%00000100 ; release the receive buffer bsr writeSJA1000 bra Send ; check for new serial data End rts ; back to monitor ; Func: returns the contents of a given register from SJA1000-CAN-Controller ; Args: X = register address ; Retn: A = data ; Dest: - readSJA1000 stx CAN_ADDR-1 ldaa CAN_DATA rts ; Func: writes a byte to a given SJA1000-CAN-Controller address ; Args: X = register address, A = new contents ; Retn: - ; Dest: - writeSJA1000 stx CAN_ADDR-1 staa CAN_DATA rts ; Func: Initialize serial communication interface SC0 (19200 baud, 8N1) ; Args: - ; Retn: - ; Dest: - initSC0 clr SC0BDH movb #$1A,SC0BDL ; set baud rate to 19200 clr SC0CR1 ; 8 data bits, 1 stop bit, no parity movb #$0C,SC0CR2 ; enable receiver and transmitter rts ; Func: Gets a byte from SC0 ; Args: - ; Retn: A = byte ; Dest: - getSC0 brclr SC0SR1,$20,getSC0 ; wait for receive data register full ldaa SC0DRL ; read out data register rts ; Func: Sends out a byte via SC0 ; Args: A = byte ; Retn: - ; Dest: - putSC0 brclr SC0SR1,$80,putSC0 ; wait until transmit data register=empty staa SC0DRL ; send new data rts -----Original Message----- From: kuinton [mailto:] Sent: Tuesday, January 20, 2004 2:36 PM To: Subject: [68HC12] CAN Programming Does anyone have any sample code to transmit and receive messages through the CAN port for the DP256 model of HC12? Please let me know... i tried to program it, but it ended up that i was using the wrong version... and the registers were all in a different place, and confusion ensued... please let me know ASAP guys. Thanks. --------------------To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu o learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu |
Reply by ●January 22, 20042004-01-22
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I wrote all this CAN stuff for the D60A which conforms to MSCAN. The D60A has an RXFG and RXBG buffer system and you will work from the RXFG buffer. The sending of messages is done with a triple buffer scheme. If this is the same as the dp256 then I can tell you that there are application notes showing the algorithm for sending using a linked list. Also there is a great source of information on this very subject in Prof. Han-way Huang's book on the 68HC12 with a lot of very good example code for the CAN module. On RXing a frame, I stuff the frame into a FIFO queue and access the messages in the main program code with another pointer. I use a separate data buffer that I use to access messages to be sent from the TX routine. After all this, I also discovered that there were critical sections in the code that needed to be made atomic - the old sink and source at different rates problem! If you need information at that particular subject there is a professor Valvano at UTexas which gives more information on his book. To be truthful the CAN site at vector-informatik.de did not really offer any appreciable amount of help because these people seem to all be working at upper levels of CAN protocols and not very many people there seem to know much about MSCAN. Then again I did find the port.de site from the CAN site and it helped me solve a rather nasty little bug that was driving me crazy when I accessed their calculator to get the bit rate constants that I needed but was calculating in error. Sydney ----- Original Message ----- From: kuinton To: Sent: Tuesday, January 20, 2004 4:36 PM Subject: [68HC12] CAN Programming Does anyone have any sample code to transmit and receive messages through the CAN port for the DP256 model of HC12? Please let me know... i tried to program it, but it ended up that i was using the wrong version... and the registers were all in a different place, and confusion ensued... please let me know ASAP guys. Thanks. --------------------To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu o learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu ---- -- Yahoo! Groups Links a.. To |
