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32180 Group User’s Manual (Rev.1.0)
CAN MODULE
13.2 CAN Module Related Registers
CRX pin
CTX pin
Self-diagnostic mode
Ack signal
generating
circuit
Rx
Tx
M32R/ECU CAN module
13.2.10 CAN Mode Registers
CAN0 Mode Register (CAN0MOD)
<Address: H
’0080 1018>CAN1 Mode Register (CAN1MOD)
<Address: H
’0080 1418>123456b7b0
CMOD
00
<After reset: H’00>
b Bit Name Function R W
0–5 No function assigned. Fix to "0". 00
6–7 CMOD 00: Normal mode R W
CAN operation mode select bit 01: Bus monitor mode
10: Self-diagnostic mode
11: Settings inhibited
(1) CMOD (CAN Operation Mode Select) bits (Bit 6, Bit 7)
These bits select the CAN operation mode.
• Normal operation mode
Normal transmit/receive operations can be performed.
• Bus monitor mode
Only receive operation is performed. During bus monitor mode, the CTX output is fixed high and neither
ACK nor an error frame can be returned.
Note: • During bus monitor mode, issuing transmit requests is inhibited. The ACK bit is handled as
“Don’t care” during bus monitor mode. Therefore, if all bits of data including the CRC delim-
iter are received normally, it is assumed that data has been received normally no matter
whether the ACK bit is high.
• Self-diagnostic mode
CTX and CRX are connected together internally in the CAN module. When combined with loopback
mode, this mode allows communication to be performed within the CAN module alone. During self-
diagnostic mode, the CTX pin output is fixed high even when transmitting.
Figure 13.2.13 Conceptual Diagram of Self-Diagnostic Mode
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