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15.1 Standby Function and Configuration
15.1.1 Standby function
The standby function is used to reduce the power consumption of the system and can be effected in the following
two modes:
(1)
HALT mode
This mode is set when the HALT instruction is executed. HALT mode stops the operation clock of the CPU.
The system clock oscillator continues oscillating. This mode does not reduce the current consumption as
much as STOP mode, but is useful for resuming processing immediately when an interrupt request is
generated, or for intermittent operations.
(2)
STOP mode
This mode is set when the STOP instruction is executed. The STOP mode stops the main system clock
oscillator and stops the entire system. The current consumption of the CPU can be substantially reduced in
this mode.
The low voltage (V
retaining the contents of the data memory at an extremely low current consumption.
STOP mode can be released by an interrupt request, so that this mode can be used for intermittent
operation. However, some time is required until the system clock oscillator stabilizes after STOP mode has
been released. If processing must be resumed immediately by using an interrupt request, therefore, use the
HALT mode.
In both modes, the previous contents of the registers, flags, and data memory before setting standby mode are all
retained. In addition, the statuses of the output latches of the I/O ports and output buffers are also retained.
Caution To set STOP mode, be sure to stop the operations of the peripheral hardware, and then execute
the STOP instruction.
148
CHAPTER 15 STANDBY FUNCTION
= 1.8 V min.) of the data memory can be retained. Therefore, this mode is useful for
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User's Manual U14826EJ5V0UD
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