7 ClOCK GeneRaTOR (ClG)
S1C17624/604/622/602/621 TeChniCal Manual
Seiko epson Corporation
7-5
V
SS
V
SS
OSC2
OSC1
X'tal1
C
G1
f
OSC1
To RTC
To peripheral
modules
OSC1EN
RTCCE
Oscillation stabilization
wait circuit
R
f1
R
D1
C
D1
SLEEP/NORMAL
3.3.2 OSC1 Oscillator Circuit (S1C17624/604)
Figure 7.
A crystal resonator (X’tal1, typ. 32.768 kHz) should be connected between the OSC1 and OSC2 pins. Additionally,
trimmer capacitor C
G1
(0 to 25 pF) should be connected between the OSC1 pin and V
SS
.
OSC1 oscillation on/off (S1C17622/602/621)
The OSC1 oscillator stops oscillating when OSC1EN/OSC_CTL register is set to 0 and starts oscillating when
set to 1. The OSC1 oscillator circuit stops oscillating in SLEEP mode.
After an initial reset, OSC1EN is set to 0, and the OSC1 oscillator circuit is halted.
OSC1 oscillation on/off (S1C17624/604)
The OSC1 oscillator stops oscillating when OSC1EN/OSC_CTL register is set to 0 and starts oscillating when
set to 1.
The OSC1 oscillator also starts oscillating by enabling the clock supply to the RTC (RTCCE/RTC_CC register
= 1) even if OSC1EN = 0.
When RTCCE = 1, the OSC1 oscillator operates even in SLEEP mode and the OSC1 clock is supplied to the
RTC for running. Note that the OSC1 clock is not supplied to other peripheral modules if OSC1EN = 0.
When RTCCE = 0, the OSC1 stops in SLEEP mode regardless of how OSC1EN is set.
After an initial reset, OSC1EN and RTCCE are both set to 0, and the OSC1 oscillator circuit is halted.
3.3.1 OSC1 Oscillator Operating Status (S1C17624/604, in normal operation)
Table 7.
OSC1en
RTCCe
OSC1 oscillator
Clock supply to
peripheral modules
Clock supply to RTC
1
1
On
On
On
1
0
On
On
Off
0
1
On
Off
On
0
0
Off
Off
Off
3.3.2 OSC1 Oscillator Operating Status (S1C17624/604, in SLEEP mode)
Table 7.
OSC1en
RTCCe
OSC1 oscillator
Clock supply to
peripheral modules
Clock supply to RTC
1
1
On
Off
On
1
0
Off
Off
Off
0
1
On
Off
On
0
0
Off
Off
Off
Stabilization wait time at start of OSC1 oscillation
The OSC1 oscillator includes an oscillation stabilization wait circuit (fixed at 256 cycles) to prevent malfunc-
tions caused by unstable clock operations at the start of OSC1 oscillation—e.g., when the OSC1 oscillator is
turned on with software. When the system clock is switched to OSC1 immediately after the OSC1 oscillator
circuit is turned on, the OSC1 clock is supplied to the system after the OSC1 clock system supply wait time
indicated below (at a maximum) has elapsed. For the oscillation start time, see the “Electrical Characteristics”
chapter.
OSC1 clock system supply wait time
≤
OSC1 oscillation start time (max.) + OSC1 oscillation stabilization
wait time (256 cycles)