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32180 Group User’s Manual (Rev.1.0)
CAN MODULE
13.6 Receiving Data Frames
13.6.3 Reading Out Received Data Frames
The following shows the procedure for reading out received data frames from the slot.
(1) Clearing the TRFIN (Transmit/Receive Finished) bit
Write H’4E, H’40 or H’00 to the CAN Message Slot Control Register (C0MSLnCNT, C1MSLnCNT) to clear
the TRFIN bit to "0". After this write, the slot operates as follows:
Values Written to CnMSLnCNT Slot Operation after Write
H’4E Operates as a data frame receive slot. Whether overwritten can be verified by ML bit.
H’40 Operates as a data frame receive slot. Whether overwritten cannot be verified by ML bit.
H’00 The slot stops transmit/receive operation.
Notes: • If message-lost check by the ML bit is needed, write H’4E to clear the TRFIN bit.
• If the TRFIN bit was cleared by writing H’4E, H’40 or H’00, it is possible that new data will be stored in the slot while
still reading out a message from it.
(2) Reading out from the message slot
Read out a message from the message slot.
(3) Checking the TRFIN (Transmit/Receive Finished) bit
Read the CAN Message Slot Control Register to check the TRFIN (Transmit/Receive Finished) bit.
1) If TRFIN (Transmit/Receive Finished) bit = "1"
It means that new data was stored in the slot while still reading out a message from it in (2) above. In this
case, the data read out in (2) may contain an undefined value. Therefore, reexecute the above
procedure beginning with clearing of the TRFIN (Transmit/Receive Finished) bit in (1).
2) If TRFIN (Transmit/Receive Finished) bit = "0"
It means that the CAN module finished reading out from the slot normally.
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