Epson S1C17624 Technical Manual page 63

7 ClOCK GeneRaTOR (ClG)
OSC3 oscillation on/off
The OSC3 oscillator circuit stops oscillating when OSC3EN/OSC_CTL register is set to 0 and starts oscillating
when set to 1. The OSC3 oscillator circuit stops oscillating in SLEEP mode.
Stabilization wait time at start of OSC3 oscillation
The OSC3 oscillator circuit includes an oscillation stabilization wait circuit to prevent malfunctions due to unsta-
ble clock operations at the start of OSC3 oscillation—e.g., when the OSC3 oscillator is turned on with software.
The OSC3 clock is not supplied to the system until the time set for this circuit has elapsed. Use OSC3WT[1:0]/
OSC_CTL register to select one of four oscillation stabilization wait times. For the oscillation start time, see the
"Electrical Characteristics" chapter.
This is set to 1,024 cycles (OSC3 clock) after an initial reset.
When the system clock is switched to OSC3 immediately after the OSC3 oscillator circuit is turned on, the
OSC3 clock is supplied to the system after the OSC3 clock system supply wait time indicated below (at a maxi-
mum) has elapsed. For the oscillation start time, see the "Electrical Characteristics" chapter.
OSC3 clock system supply wait time ≤ OSC3 oscillation start time (max.) + OSC3 oscillation
bilization wait time
note: Oscillation stability will vary, depending on the resonator and other external components. Carefully
consider the OSC3 oscillation stabilization wait time before reducing the time.
external OSC3 clock input
An external clock can be used as the OSC3 clock instead of the internal OSC3 clock described above. In this
case, leave the OSC4 pin open and input a clock via the OSC3 pin. For the input clock requirements, see the
"Electrical Characteristics" chapter.
7.3.3 OSC1 Oscillator
The OSC1 oscillator is a high-precision, low-speed oscillator circuit that uses a 32.768 kHz crystal resonator.
The OSC1 clock is generally used as the timer operation clock (for the clock timer, stopwatch timer, watchdog
timer, and 8-bit OSC1 timer) and an operation clock for the LCD driver, R/F converter, and supply voltage detector.
It can be used as the system clock instead of the IOSC or OSC3 clock to reduce power consumption when no high-
speed processing is required. The S1C17624/604 also uses OSC1 as the clock source for the RTC.
Figures 7.3.3.1 and 7.3.3.2 show the OSC1 oscillator configurations.
OSC1
C
G1
X'tal1
OSC2
V
SS
7-4
Table 7. 3.2.1 OSC3 Oscillation Stabilization Wait Time Settings
OSC3WT[1:0]
0x3
0x2
0x1
0x0
R R
f1 D1
Figure 7. 3.3.1 OSC1 Oscillator Circuit (S1C17622/602/621)
Seiko epson Corporation
Oscillation stabilization wait time
128 cycles
256 cycles
512 cycles
1024 cycles
(Default: 0x0)
OSC1EN
SLEEP/NORMAL
Oscillation stabilization
wait circuit
C
D1
V
SS
S1C17624/604/622/602/621 TeChniCal Manual
sta-
f
OSC1