
User’s Manual U16228EJ2V0UD
380
CHAPTER 19 STANDBY FUNCTION
19.1 Standby Function and Configuration
19.1.1 Standby function
Table 19-1. Relationship Between Operation Clocks in Each Operation Status
X1 Oscillator
Ring-OSC 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
Ring-OSC
Stopped
STOP
Stopped
Note 3
Stopped
HALT
Oscillating Stopped
Oscillating Oscillating Stopped
Oscillating
Note 4
Ring-OSC X1
Notes 1.
When “Cannot be stopped” is selected for Ring-OSC by a mask option.
2.
When “Can be stopped by software” is selected for Ring-OSC 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 Ring-OSC 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 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
X1 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.