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Chapter 18
AFCAN Controller
User’s Manual U16580EE3V1UD00
18.11 Power Saving Modes
18.11.1 CAN sleep mode
The CAN sleep mode can be used to set the CAN Controller to stand-by mode in order to reduce power
consumption. The CAN module can enter the CAN sleep mode from all operation modes. Release of
the CAN sleep mode returns the CAN module to exactly the same operation mode from which the CAN
sleep mode was entered.
In the CAN sleep mode, the CAN module does not transmit messages, even when transmission
requests are issued or pending.
(1)
Entering CAN sleep mode
The CPU issues a CAN sleep mode transition request by writing 01B to the PSMODE[1:0] bits of
the CnCTRL register.
This transition request is only acknowledged only under the following conditions.
(i)
The CAN module is already in one of the following operation modes
•
Normal operation mode
•
Normal operation mode with ABT
•
Receive-only mode
•
Single-shot mode
•
Self-test mode
•
CAN stop mode in all the above operation modes
(ii) The CAN bus state is bus idle (the 4th bit in the interframe space is recessive)
Note
(iii) No transmission request is pending
Note:
If the CAN bus is fixed to dominant, the request for transition to the CAN sleep mode is held
pending.Also the transition from CAN stop mode to CAN sleep mode is independent of the CAN
bus state.
Remark:
If a sleep mode request is pending, and at the same time a message is received in a mes-
sage box, the sleep mode request is not cancelled, but is executed right after message stor-
age has been finished. This may result in AFCAN being in sleep mode, while the CPU
would execute the RX interrupt routine. Therefore, the interrupt routine must check the
access to the message buffers as well as reception history list registers by using the MBON
flag, if sleep mode is used.
If any one of the conditions mentioned above is not met, the CAN module will operate as follows.
•
If the CAN sleep mode is requested from the initialization mode, the CAN sleep mode transition
request is ignored and the CAN module remains in the initialization mode.
•
If the CAN bus state is not bus idle (i.e., the CAN bus state is either transmitting or receiving) when
the CAN sleep mode is requested in one of the operation modes, immediate transition to the CAN
sleep mode is not possible. In this case, the CAN sleep mode transition request has to be held
pending until the CAN bus state becomes bus idle (the 4th bit in the interframe space is recessive).
In the time from the CAN sleep mode request to successful transition, the PSMODE[1:0] bits remain
00B. When the module has entered the CAN sleep mode, the PSMODE[1:0] bits are set to 01B.
•
If a request for transition to the initialization mode and a request for transition to the CAN sleep
mode are made at the same time while the CAN module is in one of the operation modes, the
request for the initialization mode is enabled. The CAN module enters the initialization mode at a
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Страница 534: ...534 Chapter 11 16 bit Timer Event Counter T User s Manual U16580EE3V1UD00 ...
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Страница 976: ...976 Chapter 22 Internal RAM Parity Check Function User s Manual U16580EE3V1UD00 MEMO ...
Страница 984: ...984 Chapter 23 On Chip Debug Function OCD User s Manual U16580EE3V1UD00 MEMO ...
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Страница 1036: ...1036 Chapter 27 Recommended Soldering Conditions User s Manual U16580EE3V1UD00 MEMO ...
Страница 1046: ...1046 Appendix A Index User s Manual U16580EE3V1UD00 MEMO ...
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