Receive Fifo - Infineon Technologies TC1728 User Manual

TC1728
Controller Area Network Controller (MultiCAN)

20.3.11.5 Receive FIFO

The Receive FIFO structure is used to buffer incoming (received) Remote or Data
Frames.
A Receive FIFO is selected by setting MOFCRn.MMC = 0001 in the FIFO base object.
B
This MMC code automatically designates a message object as FIFO base object. The
message modes of the FIFO slave objects are not relevant for the operation of the
Receive FIFO.
When the FIFO base object receives a frame from the CAN node it belongs to, the frame
is not stored in the base object itself but in the message object that is selected by the
base object's MOFGPRn.CUR pointer. This message object receives the CAN message
as if it is the direct receiver of the message. However, MOFCRn.MMC = 0000 is
B
implicitly assumed for the FIFO slave object, and a standard message delivery is
performed. The actual message mode (MMC setting) of the FIFO slave object is ignored.
For the slave object, no acceptance filtering takes place that checks the received frame
for a match with the identifier, IDE bit, and DIR bit.
With the reception of a CAN frame, the current pointer CUR of the base object is set to
the number of the next message object in the FIFO structure. This message object will
then be used to store the next incoming message.
If bit field MOFCRn.OVIE ("Overflow Interrupt Enable") of the FIFO base object is set and
the current pointer MOFGPRn.CUR becomes equal to MOFGPRn.SEL, a FIFO overflow
interrupt request is generated. This interrupt request is generated on interrupt node
TXINP of the base object immediately after the storage of the received frame in the slave
object. Transmit interrupts are still generated if TXIE is set.
A CAN message is stored in FIFO base and slave object only if MSGVAL = 1.
In order to avoid direct reception of a message by a slave message object, as if it was
an independent message object and not a part of a FIFO, the bit RXEN of each slave
object must be cleared. The setting of the bit RXEN is "don't care" only if the slave object
is located in a list not assigned to a CAN node.
User's Manual 20-51 V1.0, 2011-12
MultiCAN, V2.24