Datasheet

V850ES/JG3-H, V850ES/JH3-H CHAPTER 20 CAN CONTROLLER
R01UH0042EJ0500 Rev.5.00 Page 1001 of 1513
Aug 12, 2011
20.11.3 Example of using power saving modes
In some application systems, it may be necessary to place the CPU in a power saving mode to reduce the power
consumption. By using the power saving mode specific to the CAN module and the power saving mode specific to the
CPU in combination, the CPU can be woken up from the power saving status by the CAN bus.
Here is an example of using the power saving modes.
First, put the CAN module in the CAN sleep mode (PSMODE1, PSMODE0 bits = 01B). Next, put the CPU in the power
saving mode. If an edge transition from recessive to dominant is detected at the CRXD0 signal in this status, the CINTS5
bit in the CAN module is set to 1. If the C0CTRL.CIE5 bit is set to 1, a wakeup interrupt (INTC0WUP) is generated. The
CAN module is automatically released from the CAN sleep mode (PSMODE1, PSMODE0 bits = 00B) and returns to
normal operation mode (while the CAN clock is supplied, however, the PSMODE0 must be cleared by software after a bus
level change is detected at the CAN reception pin (CRXD0).). The CPU, in response to INTC0WUP, can release its own
power saving mode and return to normal operation mode.
To further reduce the power consumption of the CPU, the internal clocks, including that of the CAN module, may be
tuned off. In this case, the operating clock supplied to the CAN module is turned off after the CAN module is put in the
CAN sleep mode. Then the CPU enters a power saving mode in which the clock supplied to the CPU is turned off. If an
edge transition from recessive to dominant is detected at the CRXD0 signal in this status, the CAN module can set the
CINTS5 bit to 1 and generate a wakeup interrupt (INTC0WUP) even if it is not supplied with a clock. The other functions,
however, do not operate because the clock supply to the CAN module is shut off, and the module remains in the CAN
sleep mode. The CPU, in response to INTC0WUP, releases its power saving mode, resumes supply of the internal clocks,
including the clock to the CAN module, after oscillation stabilization time has elapsed, and starts instruction execution. The
CAN module is immediately released from the CAN sleep mode when the clock supply is resumed, and returns to normal
operation mode (PSMODE1, PSMODE0 bits = 00B).