Datasheet

© 2007 Microchip Technology Inc. Preliminary DS39625C-page 293
PIC18F2585/2680/4585/4680
REGISTER 23-21: RXERRCNT: RECEIVE ERROR COUNT REGISTER
EXAMPLE 23-5: READING A CAN MESSAGE
R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0
REC7 REC6 REC5 REC4 REC3 REC2 REC1 REC0
bit 7 bit 0
bit 7-0 REC7:REC0: Receive Error Counter bits
This register contains the receive error value as defined by the CAN specifications.
When RXERRCNT > 127, the module will go into an error-passive state. RXERRCNT does not
have the ability to put the module in “bus-off” state.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
; Need to read a pending message from RXB0 buffer.
; To receive any message, filter, mask and RXM1:RXM0 bits in RXB0CON registers must be
; programmed correctly.
;
; Make sure that there is a message pending in RXB0.
BTFSS RXB0CON, RXFUL ; Does RXB0 contain a message?
BRA NoMessage ; No. Handle this situation...
; We have verified that a message is pending in RXB0 buffer.
; If this buffer can receive both Standard or Extended Identifier messages,
; identify type of message received.
BTFSS RXB0SIDL, EXID ; Is this Extended Identifier?
BRA StandardMessage ; No. This is Standard Identifier message.
; Yes. This is Extended Identifier message.
; Read all 29-bits of Extended Identifier message.
...
; Now read all data bytes
MOVFF RXB0DO, MY_DATA_BYTE1
...
; Once entire message is read, mark the RXB0 that it is read and no longer FULL.
BCF RXB0CON, RXFUL ; This will allow CAN Module to load new messages
; into this buffer.
...