Transmission Using Transmit Queues; Transmit History Function - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
21.7.4

Transmission Using Transmit Queues

Three to sixteen buffers are allocated to a transmit queue for each channel, and transmit buffer ((16 ×
m) + 15) is used as an access window of a corresponding channel.
All messages in a transmit queue are targets of transmit priority determination and are transmitted in
the ID priority order regardless of storage sequence. If two messages having the same ID are stored in a
transmit queue, these messages are not always transmitted in the order of their storage in the transmit
queue.
Setting the TXQE bit in the RSCAN0TXQCCm register to 0 disables transmit queues. When the
TXQE bit is set to 0, the TXQEMP flag in the RSCAN0TXQSTSm register is set to 1 (the transmit
queue contains no messages (transmit queue empty)) at the timing below.
• The transmit queue becomes empty immediately when no message in it is being transmitted or
will be transmitted next.
• The transmit queue becomes empty after transmission completion, CAN bus error detection, or
arbitration-lost when a message in it is being transmitted or will be transmitted next.
When the TXQE bit is cleared to 0, all messages in transmit queues are lost and messages cannot be
stored in transmit queues. Confirm that the TXQEMP flag is set to 1 before setting the TXQE bit to 1
again.
21.7.5

Transmit History Function

Information about transmitted messages can be stored in the transmit history buffer. Each channel has a
single transmit history buffer that can contain 16 sets of transmit history data.
A message transmit source buffer type can be selected by the THLDTE bit in the RSCAN0THLCCm
register. The THLEN bit in the RSCAN0CFIDk register (k = 0 to 5) determines whether transmit
history data is stored for each message.
The following information on a transmitted message will be stored in the transmission history buffer
after the successful completion of transmission.
Storage of the transmission history data after the successful completion of transmission may take up to
144 cycles of pclk.
• Buffer type
• Buffer number
• Label data
R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
001 : Transmit buffer
B
010 : Transmit/receive FIFO buffer
B
100 : Transmit queue
B
Number of source transmit buffer, transmit queue, or transmit/receive
FIFO buffer.
This number depends on buffer types. See Table 21.90.
Label information of the transmit message
21. CAN Interface
21-135