FD controller area network (FDCAN) RM0444
1222/1390 RM0444 Rev 5
36.3.6 FDCAN Tx Buffer element
The Tx Buffers section (three elements) can be configured to hold Tx FIFO or Tx Queue.
The Tx Handler distinguishes between Tx FIFO and Tx Queue using the Tx Buffer
configuration FDCAN_TXBC.TFQM . The element size is configured for storage of CAN FD
messages with up to 64 bytes data.
Rn Bits 23:16
DBm-1[7:0]
Data Byte m-1
Rn Bits 15:8
DBm-2[7:0]
Data Byte m-2
Rn Bits 7:0
DBm-3[7:0]
Data Byte m-3
Table 206. Rx FIFO element description (continued)
Field Description
Table 207. Tx Buffer and FIFO element
Bit 31 2423 1615 87 0
T0 ESI XTD RTR ID[28:0]
T1 MM[7:0] EFC Res. FDF BPS DLC[3:0] Res.
T2 DB3[7:0] DB2[7:0] DB1[7:0] D[7:0]
T3 DB7[7:0] DB6[7:0] DB5[7:0] DB4[7:0]
...
...
...
...
Tn DBm[7:0] DBm-1[7:0] DBm-2[7:0] DBm-3[7:0]
Table 208. Tx Buffer element description
Field Description
T0 Bit 31
ESI
(1)
Error state indicator
– 0: ESI bit in CAN FD format depends only on error passive flag
– 1: ESI bit in CAN FD format transmitted recessive
T0 Bit 30
XTD
Extended identifier
– 0: 11-bit standard identifier
– 1: 29-bit extended identifier
T0 Bit 29
RTR
(2)
Remote transmission request
– 0: Transmit data frame
– 1: Transmit remote frame
T0 Bits 28:0
ID[28:0]
Identifier
Standard or extended identifier depending on bit XTD. A standard identifier has to be
written to ID[28:18].
T1 Bits 31:24
MM[7:0]
Message marker
Written by CPU during Tx Buffer configuration. Copied into Tx Event FIFO element for
identification of Tx message status.
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