Transmission Functions - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
21.7

Transmission Functions

There are three types of transmission.
• Transmission using transmit buffers:
Each channel has 16 buffers.
• Transmission using transmit/receive FIFO buffers (transmit mode):
Each channel has three FIFO buffers. Up to 96 messages can be contained in a single FIFO buffer.
Each FIFO buffer is used with a link to a transmit buffer. Only the message to be transmitted next
in a FIFO buffer becomes the target of transmit priority determination. Messages are transmitted
sequentially on a first-in, first-out basis.
• Transmission using transmit queues:
Up to 16 transmit buffers per channel can be allocated to the transmit queues. Transmit buffer ((16
× m) + 15) is used as an access window of a corresponding channel. Transmit buffers are allocated
to transmit queues in descending order of buffer number. All messages in transmit queues, which
are targets of priority determination, are transmitted in the order of ID number.
Figure 21.9 shows the allocation of transmit queues and transmit/receive FIFO buffer link.
Transmit buffer 0
Transmit buffer 1
Transmit buffer 2
Transmit buffer 3
Transmit buffer 4
Transmit buffer 5
Transmit buffer 6
Transmit buffer 7
Transmit buffer 8
Transmit buffer 9
Transmit buffer 10
Transmit buffer 11
Transmit buffer 12
Transmit buffer 13
Transmit buffer 14
Transmit buffer 15
Only transmit buffers are used
Figure 21.9
R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
Transmit buffer 0
Transmit/receive FIFO buffer 0
Transmit buffer 2
Transmit/receive FIFO buffer 1
Transmit buffer 4
Transmit buffer 5
Transmit buffer 6
Transmit buffer 7
Transmit buffer 8
Transmit buffer 9
Transmit buffer 10
Transmit buffer 11
Transmit buffer 12
Transmit buffer 13
Transmit buffer 14
Transmit/receive FIFO buffer 2
Transmit buffers and transmit/
receive FIFO buffers are used
(Transmit/receive FIFO
buffers are linked to transmit
buffers 1, 3, and 15)
Allocation of Transmit Queues and Transmit/Receive FIFO Buffer Links
Transmit/receive FIFO buffer 0
Transmit buffer 1
Transmit buffer 2
Transmit buffer 3
Transmit buffer 4
Transmit/receive FIFO buffer 1
Transmit buffer 6
Transmit buffer 7
Transmit buffer 8
Transmit buffer 9
Transmit buffer 10
Transmit/receive FIFO buffer 2
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit buffers, transmit/
receive FIFO buffers, and a
transmit queue Is used
(Transmit/receive FIFO buffers
are linked to transmit buffers
0, 5, and 11; Four transmit
queue elements are allocated
to transmit buffers)
21. CAN Interface
Transmit buffer 0
Transmit buffer 1
Transmit buffer 2
Transmit buffer 3
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit queue
Transmit buffers and a
transmit queue is used (12
transmit queue elements
are allocated to transmit
buffers)
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