HD6432621 Hitachi, HD6432621 Datasheet - Page 624

• Manufacturer Part Number: HD6432621
• Description: (HD64F262x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

4. Error counters
5. Register access
6. HCAN medium-speed mode
7. Register retention during standby
8. Using bit operation instructions
9. HTxD pin output in error passive state
10. Transition to HCAN sleep mode
11. Message transmission cancellation (TxCR)
12. TxCR in the bus off state
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In the case of error active and error passive, REC and TEC normally count up and down. In the
bus off state, 11-bit recessive sequences are counted (REC + 1) using REC. If REC reaches 96
during the count, IRR4 and GSR1 are set, and if REC reaches 128, IRR7 is set.
Byte or word access can be used on all HCAN registers. Longword access cannot be used.
HCAN registers cannot be read or written to in medium-speed mode.
All HCAN registers are initialized in hardware standby mode and software standby mode.
Start flags in HCAN are cleared by writing 1 to them; there is no need to use bit operation
instructions to clear them. To clear a flag, use the MOV instruction to write a 1 to the bit to be
cleared.
If the HRxD pin becomes fixed at 1 during message transmission or reception when the HCAN
is in the error active state, the HTxD pin will output 0 continuously while in the error passive
state. To stop continuous 0 output to the CAN bus, disable the HCAN by means of an error
warning interrupt or by setting the HCAN module stop mode through detection of a fixed 1
state by the HxRD pin monitor.
The HCAN stops (transmission/reception stops) when MCR0 is cleared to 0 immediately after
an HCAN sleep mode transition effected by setting TXPR of the HCAN to 1 and setting
MCR5 to 1. When a transition is made to the HCAN sleep mode by means of the above steps,
a 10-cycle wait should be inserted after the TxPR setting. After an HCAN sleep mode
transition, release the HCAN sleep mode by clearing MCR5 to 0.
If all the following conditions are met when cancellation of a transmission message is
performed by means of TxCR of the HCAN, the TxCR or TxPR bit indicating cancellation is
not cleared even though internal transmission is canceled.
When canceling a message using TxCR, 1 should be written continuously until TxCR or TxPR
becomes 0.
If TxPR is set before the HCAN goes to the bus off state, and a transition is made to the bus off
state with transmission incomplete, cancellation will be performed even if TxCR is set during
the bus off period, and the message will be transmitted after a transition to the error active
state.