Power Save Mode Activation - NEC V850ES/F 3-L Series User Manual

Clock Generator

4.4.5 Power save mode activation

(1)
(2)
Example
In the following procedures are described how to securely entering a power
save mode.
HALT mode
For entering the HALT mode proceed as follows:
1. Mask all interrupts which shall not have wake-up capability by
xxIC.xxMK = 0 and discard all possibly pending interrupts by xxIC.xxIF = 0.
2. Unmask all interrupts which shall have wake-up capability by
xxIC.xxMK = 1.
3. Execute the "halt" instruction.
IDLE1, IDLE2 and STOP mode
For entering these power save mode proceed as follows:
1. In case maskable interrupts shall be used for wake-up unmask these
interrupts by IMRm.xxMK = 0 (refer to "IMRm - Interrupt mask registers" on
page 240).
2. Mask all other interrupts, i.e.
– none wake-up capable interrupts
– wake-up capable interrupts which shall not be used for wake-up
by IMRm.xxMK = 1. This prevents the power save mode entry procedure
from being interrupted by these interrupts.
3. It is recommended to disable interrupt acknowledgement by the "di"
instruction.
4. Specify the desired power save mode in PSM.PSM[1:0].
5. Enable writing to the write-protected register PSC by writing to PRCMD.
6. Write to PSC for specifying permitted wake-up events and activate the
power save mode by setting PSC.STP to 1.
The following example shows how to initialize and enter a IDLE1, IDLE2 or
STOP power save mode.
First the desired power save mode is specified (IDLE2 mode in this example,
that means PSMR.PSM[1:0] = 10
The PSC register is a write-protected register, and the PRCMD register is the
corresponding write-enable register. PRCMD has to be written immediately
before writing to PSC.
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Chapter 4
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