
CHAPTER 8 CLOCK GENERATOR FUNCTIONS
User’s Manual U12688EJ4V0UM00
235
8.5
Power Saving Control
8.5.1 Outline
The V850E/MS1 standby function comprises the following three modes:
(1) HALT mode
In this mode, the clock generator (oscillator and PLL synthesizer) continues to operate, but the CPU’s
operation clock stops. Supply of the clock to the other internal peripheral functions is continued. Through
intermittent operation by combining with the normal operating mode, the system’s total power consumption
can be reduced.
The system is switched to the HALT mode via an exclusive instruction (the HALT instruction).
(2) IDLE mode
In this mode, the clock generator (oscillator and PLL synthesizer) continues to operate, but supply of the
internal system clock is stopped, which causes the system overall to stop.
When releasing the system from the IDLE mode, it is not necessary to secure the oscillation stabilization time
of the oscillator, so it is possible to switch to normal operation at high speed.
The system enters the IDLE mode in accordance with the settings in the PSC register (specific register).
The IDLE mode is positioned midway between the software STOP mode and the HALT mode in relation to
clock stabilization time and current consumption and is used for cases where the low current consumption
mode is used and where it is desired to eliminate the clock stabilization time after it is released.
(3) Software STOP mode
In this mode, the clock generator (oscillator and PLL synthesizer) is stopped and the system overall is
stopped, thus entering an ultra-low power consumption state where only leak current is lost.
It is possible to enter the software STOP mode by setting the PSC register (specific register).
(a) When in the PLL Mode
By setting the register by software, you can enter the software STOP mode. At the same time the
oscillator stops, the PLL synthesizer’s clock output stops. After releasing the software STOP mode, it is
necessary to secure oscillation stabilization time for the oscillator for a period of time until the system
clock stabilizes. Also, depending on the program, PLL lockup time may be required.
(4) Clock output inhibit mode
Internal system clock output from the CLKOUT pin is prohibited.
The operation of the clock generator in normal operation, and in the HALT, IDLE, and software STOP modes is
shown in Table 8-1.
By combining each of the modes and by switching modes according to the required usage, it is possible to realize
an effective low power consumption system.
Содержание V850E/MS1 UPD703100
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