PIC18F2480/2580/4480/4580
EXAMPLE 24-3:
TRANSMITTING A CAN MESSAGE USING BANKED METHOD
; Need to transmit Standard Identifier message 123h using TXB0 buffer.
; To successfully transmit, CAN module must be either in Normal or Loopback mode.
; TXB0 buffer is not in access bank. And since we want banked method, we need to make sure
; that correct bank is selected.
BANKSEL TXB0CON
; One BANKSEL in beginning will make sure that we are
; in correct bank for rest of the buffer access.
; Now load transmit data into TXB0 buffer.
MOVLW
MOVWF
MY_DATA_BYTE1
TXB0D0
; Load first data byte into buffer
; Compiler will automatically set “BANKED” bit
; Load rest of data bytes - up to 8 bytes into TXB0 buffer.
...
; Load message identifier
MOVLW
MOVWF
MOVLW
MOVWF
60H
TXB0SIDL
24H
; Load SID2:SID0, EXIDE = 0
; Load SID10:SID3
TXB0SIDH
; No need to load TXB0EIDL:TXB0EIDH, as we are transmitting Standard Identifier Message only.
; Now that all data bytes are loaded, mark it for transmission.
MOVLW
MOVWF
B’00001000’
TXB0CON
; Normal priority; Request transmission
; If required, wait for message to get transmitted
BTFSC
BRA
TXB0CON, TXREQ
$-2
; Is it transmitted?
; No. Continue to wait...
; Message is transmitted.
EXAMPLE 24-4:
TRANSMITTING A CAN MESSAGE USING WIN BITS
; Need to transmit Standard Identifier message 123h using TXB0 buffer.
; To successfully transmit, CAN module must be either in Normal or Loopback mode.
; TXB0 buffer is not in access bank. Use WIN bits to map it to RXB0 area.
MOVF
CANCON, W
; WIN bits are in lower 4 bits only. Read CANCON
; register to preserve all other bits. If operation
; mode is already known, there is no need to preserve
; other bits.
ANDLW
IORLW
MOVWF
B’11110000’
B’00001000’
CANCON
; Clear WIN bits.
; Select Transmit Buffer 0
; Apply the changes.
; Now TXB0 is mapped in place of RXB0. All future access to RXB0 registers will actually
; yield TXB0 register values.
; Load transmit data into TXB0 buffer.
MOVLW
MOVWF
MY_DATA_BYTE1
RXB0D0
; Load first data byte into buffer
; Access TXB0D0 via RXB0D0 address.
; Load rest of the data bytes - up to 8 bytes into “TXB0” buffer using RXB0 registers.
...
; Load message identifier
MOVLW
MOVWF
MOVLW
MOVWF
60H
RXB0SIDL
24H
; Load SID2:SID0, EXIDE = 0
; Load SID10:SID3
RXB0SIDH
; No need to load RXB0EIDL:RXB0EIDH, as we are transmitting Standard Identifier Message only.
; Now that all data bytes are loaded, mark it for transmission.
MOVLW
MOVWF
B’00001000’
RXB0CON
; Normal priority; Request transmission
; If required, wait for message to get transmitted
BTFSC
BRA
RXB0CON, TXREQ
$-2
; Is it transmitted?
; No. Continue to wait...
; Message is transmitted.
; If required, reset the WIN bits to default state.
DS39637D-page 292
© 2009 Microchip Technology Inc.
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