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User’s Manual U16315EJ3V1UD
347
CHAPTER 18 STANDBY FUNCTION
18.1 Standby Function and Configuration
18.1.1 Standby function
Table 18-1. Relationship Between Operation Clocks in Each Operation Status
X1 Oscillator
Internal Oscillator
Prescaler Clock
Supplied to Peripherals
Note 2
Status
Operation
Mode
MSTOP = 0
MCC = 0
MSTOP = 1
MCC = 1
Note 1
RSTOP = 0 RSTOP = 1
Subsystem
Clock
Oscillator
CPU Clock
After
Release
MCM0 = 0
MCM0 = 1
Reset
Stopped
Internal
oscillation
Stopped
STOP
Stopped
Note 3
Stopped
HALT
Oscillating
Stopped
Oscillating
Stopped
Oscillating
Note 4
Internal
oscillation
X1
Notes 1.
When “Cannot be stopped” is selected for the internal oscillator by a mask option.
2.
When “Can be stopped by software” is selected for the internal oscillator by a mask option.
3.
Operates using the CPU clock at STOP instruction execution.
4.
Operates using the CPU clock at HALT instruction execution.
Caution
The RSTOP setting is valid only when “Can be stopped by software” is set for the internal oscillator
by a mask option.
Remark
MSTOP: Bit 7 of the main OSC control register (MOC)
MCC:
Bit 7 of the processor clock control register (PCC)
RSTOP: Bit 0 of the internal oscillation mode register (RCM)
MCM0:
Bit 0 of the main clock mode register (MCM)
The standby function is designed to reduce the operating current 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 is stopped. If the
X1 oscillator, internal oscillator, or subsystem clock oscillator is operating before the HALT mode is set, oscillation
of each clock continues. In this mode, the operating current is not decreased as much as in the STOP mode, but
the HALT mode is effective for restarting operation immediately upon interrupt request generation and carrying
out intermittent operations.