XC164-16 Datasheet, PDF (321/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
TwinCAN Module
21.1.4.4 Handling of Receive Message Objects
A message object with direction flag DIR = ‘0’ (message configuration register
MSGCFGn) is handled as receive object.
In the initialization phase, the transmit request bitfield (TXRQ), the message lost bitfield
(MSGLST) and the NEWDAT bitfield in register MSGCTR should be reset.
All message objects with bitfield MSGVAL = ‘10’ are operable and taken into account by
the CAN node controller operation described below.
When a data frame has been received, the new information is stored in the data partition
of the message object (MSGDRn0, MSGDRn4) and the bitfield DLC in register
MSGCFG is updated with the number of received bytes. Unused message bytes will be
overwritten by non-specified values. If the NEWDAT bitfield in register MSGCTR is still
set, the CAN controller assumes an overwrite of the previously stored message and
signals a data loss by setting bitfield MSGLST. In any case, bitfield NEWDAT is
automatically set to ‘10’ reporting an update of the data register by the CAN controller.
The captured value of the frame counter is copied to bitfield CFCVAL in register
MSGCTRn and a receive interrupt request is generated (INTPNDn and RXIPNDn are
set) if enabled by RXIE = ‘10’. Then the frame counter is incremented by one if enabled
in control register AFCR/BFCR.
When a receive object is marked to be transmitted (TXRQ = ‘10’), bit MSGLST changes
automatically to CPUUPD. If CPUUPD is reset to ‘01’, the CAN controller generates a
remote frame which is emitted to the other communication partners via CAN bus. In case
of CPUUPD = ‘10’, the remote frame transfer is prohibited until the CPU releases the
pending transmission by resetting CPUUPD to ‘01’. RMTPND and TXRQ are
automatically reset, when the remote frame has been successfully transmitted. Finally,
a transmit interrupt request is generated if enabled by TXIE = ‘10’.
When a remote frame with matching identifier is received, it is not answered and not
indicated by an interrupt request.
User’s Manual
TwinCAN_X41, V2.1
21-21
V2.1, 2004-03