Espressif ESP32 Technical Reference Manual page 568

21 Two-wire Automotive Interface (TWAI)
Bit SEG.4 Bit SEG.3
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
Notes:
• Bit RTR: under Standard Frame Format.
• Identifier Extension Bit: 0 for Standard Frame Format.
21.5.9 Arbitration Lost Capture
The Arbitration Lost Capture (ALC) feature allows the TWAI controller to record the bit position where it loses
arbitration. When the TWAI controller loses arbitration, the bit position is recorded in the
CAP_REG and the Arbitration Lost Interrupt is triggered.
Subsequent loses in arbitration will trigger the Arbitration Lost Interrupt, but will not be recorded in the
LOST CAP_REG until the current Arbitration Lost Capture is read from the TWAI_ERR_CODE_CAP_REG.
Table 21-18 illustrates the bit fields of the
tions of a TWAI message.
Table 21-18. Bit Information of
Bit 31-5 Bit 4
Reserved BITNO.4
Notes:
• BITNO: Bit Number (BITNO) indicates the nth bit of a TWAI message where arbitration was lost.
21.6 Register Summary
Name
Configuration Registers
TWAI_MODE_REG
Espressif Systems
Bit SEG.2
1 1
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
0 0
0 0
0 1
0 0
0 1
1 1
TWAI_ERR_CODE_CAP_REG
TWAI_ARB LOST
Bit 3
1 1
BITNO.3
Description
Mode Register
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Bit SEG.1 Bit SEG.0
0 1
0 1
1 1
1 0
0 0
0 0
0 1
1 1
1 0
1 0
0 1
1 0
1 1
1 1
0 0
whilst Figure
CAP_REG; TWAI Address 0x2c
Bit 2 Bit 1
1
BITNO.2 BITNO.1
568
Description
reserved bit 1
reserved bit 0
data length code
data field
CRC sequence
CRC delimeter
acknowledge slot
acknowledge delimeter
end of frame
intermission
active error flag
passive error flag
tolerate dominant bits
error delimeter
overload flag
TWAI_ARB LOST
TWAI_ARB
21-11 illustrates the bit posi-
Bit 0
1 1
BITNO.0
Address Access
0x3FF6B000 R/W
ESP32 TRM (Version 5.2)