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GD32A50x User Manual
604
2[7:0]
3[7:0]
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Bits
Fields
Descriptions
31:24
DATA_i[7:0]
Data byte i (i = 4*x - 8)
Refer to 3[7:0] descriptions.
23:16
1[7:0]
Data byte i+1 (i = 4*x - 8)
Refer to 3[7:0] descriptions.
15:8
2[7:0]
Data byte i+2 (i = 4*x - 8)
Refer to 3[7:0] descriptions.
7:0
3[7:0]
Data byte i+3 (i = 4*x - 8)
Up to 64 bytes can be used for a data frame, depending on the DLC value of the
mailbox.
For Rx frames, the data received from the CAN bus are stored in this bit field.
Mailbox number
When Rx FIFO is disabled, the dedicated RAM space is occupied by mailboxes only, so the
mailbox number is the descriptor number which is incremented by one each time when across
the complete mailbox descriptor length (with 8, 16, 32, or 64 data bytes).
When Rx FIFO is enabled (CAN FD mode disabled, data field is 8-byte length), the dedicated
RAM space is occupied by both mailboxes and FIFO, so uniformly count the descriptor
number by a mailbox descriptor length with 8 data bytes, then the mailbox number is the
descriptor number which is occupied by mailbox.
Mailbox size for CAN FD
When CAN FD is enabled, the size of mailboxes that the CAN 512 bytes RAM can be
partitioned is configured by MDSZ[1:0] bits in CAN_FDCTL register.
Table 23-5.
Mailbox size
MDSZ[1:0]
Payload size in bytes
Mailbox size
0b00
8
32
0b01
16
21
0b10
32
12
0b11
64
7
23.3.2.
Rx FIFO descriptor
The Rx FIFO descriptor is shown in
When RFEN bit in CAN_CTL0 register is 1, the RAM space which normally occupied by
mailbox 0
–5 with 8 byte payload is used for the Rx FIFO. FDES0 – FDES3 contains the output