7 CLOCK GENERATOR (CLG)
7-6
Seiko Epson Corporation
S1C17651 TECHNICAL MANUAL
When RTCRUN and OSC1EN are both set to 1, the OSC1 oscillator continues operating if the system enters
SLEEP mode.
When RTCRUN = 0, the OSC1 stops in SLEEP mode regardless of how OSC1EN is set.
After an initial reset, OSC1EN and RTCRUN are both set to 0, and the OSC1 oscillator circuit is halted.
3.3.1 OSC1 Oscillator Operating Status (normal operation)
Table 7.
OSC1EN
RTCRUN
OSC1 oscillator
1
On
1
0
On
0
1
Off
0
Off
3.3.2 OSC1 Oscillator Operating Status (SLEEP mode)
Table 7.
OSC1EN
RTCRUN
OSC1 oscillator
1
On
1
0
Off
0
1
Off
0
Off
Stabilization wait time at start of OSC1 oscillation
The OSC1 oscillator circuit includes an oscillation stabilization wait circuit to prevent malfunctions due to unsta-
ble clock operations at the start of OSC1 oscillation—e.g., when the OSC1 oscillator is turned on with software.
The OSC1 clock is not supplied to the system until the time set for this circuit has elapsed. Use OSC1AWT[1:0]/
CLG_WAIT register to select one of four OSC1A oscillation stabilization wait times. Use OSC1BWT[1:0]/
CLG_WAIT register for OSC1B. For the oscillation start time, see the “Electrical Characteristics” chapter.
3.3.3 OSC1A Oscillation Stabilization Wait Time Settings
Table 7.
OSC1AWT[1:0]
Oscillation stabilization wait time
0x3
2048 cycles
0x2
4096 cycles
0x1
8192 cycles
0x0
16384 cycles
(Default: 0x0)
3.3.4 OSC1B Oscillation Stabilization Wait Time Settings
Table 7.
OSC1BWT[1:0]
Oscillation stabilization wait time
0x3
8 cycles
0x2
16 cycles
0x1
32 cycles
0x0
64 cycles
(Default: 0x0)
This is set to 16384 cycles (OSC1 clock) when OSC1A is selected or 64 cycles when OSC1B is selected after
an initial reset.
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 maxi-
mum) 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 sta-
bilization wait time
Notes: Oscillation stability will vary, depending on the resonator and other external components.
Carefully consider the OSC1A oscillation stabilization wait time before reducing the time.
Be sure to avoid turning the OSC1A or OSC1B oscillator off for at least four seconds from
start of oscillation after the oscillator is turned on. For the oscillation start time, see the “Electrical
Characteristics” chapter.
The OSC1B oscillation frequency will be higher than the value that is described in the “Electrical
Characteristics” chapter for about 3 ms immediately after turning the OSC1B oscillator on.