Datasheet

Section 6 Power-Down Modes
Rev.5.00 Nov. 02, 2005 Page 76 of 500
REJ09B0027-0500
6.1.1 System Control Register 1 (SYSCR1)
SYSCR1 controls the power-down modes, as well as SYSCR2.
Bit Bit Name
Initial
Value R/W Description
7 SSBY 0 R/W Software Standby
This bit selects the mode to transit after the execution of
the SLEEP instruction.
0: Enters sleep mode or subsleep mode.
1: Enters standby mode.
For details, see table 6.2.
6
5
4
STS2
STS1
STS0
0
0
0
R/W
R/W
R/W
Standby Timer Select 2 to 0
These bits designate the time the CPU and peripheral
modules wait for stable clock operation after exiting from
standby mode, subactive mode, or subsleep mode to
active mode or sleep mode due to an interrupt. The
designation should be made according to the clock
frequency so that the waiting time is at least 6.5 ms. The
relationship between the specified value and the number
of wait states is shown in table 6.1. When an external
clock is to be used, the minimum value (STS2 = STS1 =
STS0 =1) is recommended.
3 NESEL 0 R/W Noise Elimination Sampling Frequency Select
The subclock pulse generator generates the watch clock
signal (φ
W
) and the system clock pulse generator
generates the oscillator clock (φ
OSC
). This bit selects the
sampling frequency of the oscillator clock when the watch
clock signal (φ
W
) is sampled. When φ
OSC
= 4 to 20 MHz,
clear NESEL to 0.
0: Sampling rate is φ
OSC
/16
1: Sampling rate is φ
OSC
/4
2 to 0  All 0  Reserved
These bits are always read as 0.