
CHAPTER 19 CAN CONTROLLER
Preliminary User’s Manual U16541EJ1V0UM
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19.11 Power Saving Modes
19.11.1 CAN sleep mode
The CAN sleep mode can be used to set the CAN controller to standby mode in order to reduce power
consumption. The CAN sleep mode can be entered from all operational modes of the CAN module. A release of the
CAN sleep mode returns the CAN module to exactly the same operational mode from which the CAN sleep mode was
entered.
In the CAN sleep mode, the CAN module does not transmit messages, even when transmit requests are issued or
pending.
(1) Entering CAN sleep mode
The CPU issues a CAN sleep mode transition request by writing 01B to the PSMODE1, PSMODE0 bit string in
the C0CTRL register.
That transition request is only accepted under the following conditions.
(i) The CAN module is already in one of the following operational modes.
“Normal operating mode”
“Normal operating mode with automatic block transmission”
“Receive-only mode”
“Single-shot mode”
“Self-test mode”
“CAN Stop mode”
(ii) The CAN bus state is bus idle.
If one of the conditions mentioned above is not met, the CAN module will operate as follows.
If CAN sleep mode is requested from INIT mode, the CAN sleep mode transition request is ignored and the CAN
module remains in INIT mode.
If the CAN bus state is not bus idle (i.e., the CAN bus state is either “transmitting” or “receiving”) when CAN sleep
mode is requested, immediate transition to CAN sleep mode is not possible. The CAN sleep mode transition
request has to be held pending until the CAN bus state becomes bus idle. In the time from CAN sleep mode
transition request to successful transition, the PSMODE1, PSMOD0 bit string remains 00H.
(2) Releasing CAN sleep mode
The CAN sleep mode is released by the following events.
When the CPU writes 00B to the PSMODE1, PSMODE0 bit string in the C0CTRL register.
A falling edge on the CAN0RX pin (i.e., the CAN bus level shifts from recessive to dominant)
After releasing the CAN sleep mode, the CAN module returns to the operational mode from which CAN sleep
mode was requested and PSMODE1, PSMODE0 in the C0CTRL register are reset to 00B.
The interrupt status bit CINTS5 in the C0INTS register is also set (1), if the interrupt enable bit CIE5 is set (1).
When INIT mode is requested while the CAN module is in CAN sleep mode, that request is ignored; the CPU has to
release sleep mode first before entering the INIT mode.
19.11.2 CAN stop mode
The CAN stop mode can be used to set the CAN controller to standby mode to reduce power consumption, but
without the ability to wake up again autonomously. The CAN stop mode can only be entered from the CAN sleep
mode of the CAN module. A release of the CAN stop mode puts the CAN module in the sleep mode. In the CAN
stop mode, the CAN module does not transmit messages, even when transmit requests are issued or pending.