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19.1 Standby Function and Configuration
19.1.1 Standby function
Table 19-1. Relationship Between Operation Clocks in Each Operation Status
Status
High-Speed System
Clock Oscillator
MSTOP = 0
Operation
MCC = 0
Mode
Reset
Stopped
STOP
HALT
Oscillating
Notes 1.
When "Cannot be stopped" is selected for Ring-OSC by the option byte.
2.
When "Can be stopped by software" is selected for Ring-OSC by the option byte.
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 Ring-OSC by the
option byte.
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 Ring-OSC 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
high-speed system clock oscillator, Ring-OSC 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.
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CHAPTER 19 STANDBY FUNCTION
Ring-OSC Oscillator
MSTOP = 1
Note 1
MCC = 1
RSTOP = 0 RSTOP = 1
Stopped
Oscillating
Oscillating
Stopped
User's Manual U16899EJ2V0UD
Subsystem
Clock
Oscillator
Note 2
Oscillating
Stopped
CPU Clock
Prescaler Clock
After
Supplied to Peripherals
Release
MCM0 = 0
MCM0 = 1
Ring-OSC
Stopped
Note 3
Stopped
Note 4
Ring-OSC
High-
speed
system
clock
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