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17.1 Standby Function and Configuration
17.1.1 Standby function
The standby function is used to decrease the power consumption of the system. The following two modes
are available.
(1) HALT mode
HALT instruction execution sets the HALT mode. In the HALT mode, the CPU operation clock stops. The
system clock oscillator continues oscillation. In this mode, the power consumption cannot be decreased
as much as in the STOP mode, but the HALT mode is effective for restarting immediately upon interrupt
request and carrying out intermittent operations like clock operations.
(2) STOP mode
STOP instruction execution sets the STOP mode. In the STOP mode, the main system clock oscillator
stops and the whole system stops, so the CPU power consumption can be considerably decreased.
Data memory low-voltage hold (down to V
holding data memory contents with ultra-low power consumption.
Because this mode can be released by an interrupt request, it enables intermittent operations to be carried
out. However, because a wait time is necessary to secure the oscillation stabilization time after the STOP
mode is released, select the HALT mode if it is necessary to start processing immediately upon interrupt
request.
In either mode, all the contents of the registers, flags, and data memory just before standby mode is set are
held. The I/O port output latch and output buffer statuses are also held.
Cautions 1. The STOP mode can be used only when the system operates with the main system clock
(subsystem clock oscillation cannot be stopped).
either the main system clock or the subsystem clock.
2. When proceeding to the STOP mode, be sure to stop the peripheral hardware operation
operated with the main system clock and execute the STOP instruction.
3. To reduce the power consumption of the A/D converter, set bit 7 (CS) of the A/D converter
mode register (ADM) to 0 to stop the A/D converter's operation before executing the HALT
or STOP instruction.
CHAPTER 17 STANDBY FUNCTION
= 2 V) is possible. Thus, the STOP mode is effective for
DD
User's Manual U11302EJ4V0UM
The HALT mode can be used with
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