7 ClOCK GeneRaTOR (ClG)
S1C17624/604/622/602/621 TeChniCal Manual
Seiko epson Corporation
7-3
Oscillation enable bit
(IOSCEN/OSC3EN/OSC1EN)
Oscillation waveform
Digitized oscillation waveform
Oscillator output clock
(f
IOSC
/f
OSC3
/f
OSC1
)
System supply wait time
Oscillation start time
Oscillation stabilization wait time
3.1.2 Oscillation Start Time and Oscillation Stabilization Wait Time
Figure 7.
The IOSC clock is not supplied to the system until the time set for this circuit has elapsed. Use IOSCWT[1:0]/
OSC_CTL register to select one of four oscillation stabilization wait times.
3.1.1 IOSC Oscillation Stabilization Wait Time Settings
Table 7.
iOSCWT[1:0]
Oscillation stabilization wait time
0x3
8 cycles
0x2
16 cycles
0x1
32 cycles
0x0
64 cycles
(Default: 0x0)
This is set to 64 cycles (IOSC clock) after an initial reset. This means the CPU can start operating when the
CPU operation start time at initial reset indicated below (at a maximum) has elapsed after the reset state is can-
celed. For the oscillation start time, see the “Electrical Characteristics” chapter.
CPU operation start time at initial reset
≤
IOSC oscillation start time (max.) + IOSC oscillation stabilization
wait time (64 cycles)
When the system clock is switched to IOSC immediately after turning the IOSC oscillator on, the IOSC clock
is supplied to the system after the IOSC clock system supply wait time indicated below (at a maximum) has
elapsed. If the power supply voltage V
DD
has stabilized sufficiently, IOSCWT[1:0] can be set to 0x3 to reduce
the oscillation stabilization wait time.
IOSC clock system supply wait time
≤
IOSC oscillation start time (max.) + IOSC oscillation stabilization
wait time
OSC3 Oscillator
7.3.2
The OSC3 oscillator is a high-precision, high-speed oscillator circuit that uses either a crystal resonator or a ceramic
resonator. It can be switched for use with the IOSC oscillator. Figure 7.3.2.1 shows the OSC3 oscillator configuration.
V
SS
OSC4
OSC3
R
f3
R
D3
C
D3
C
G3
SLEEP/NORMAL
X'tal3
or
Ceramic
f
OSC3
OSC3EN
Oscillation stabilization
wait circuit
OSC3WT[1:0]
3.2.1 OSC3 Oscillator Circuit
Figure 7.
A crystal resonator (X’tal3) or a ceramic resonator (Ceramic) and a feedback resistor (R
f3
) should be connected
between the OSC3 and OSC4 pins. Additionally, two capacitors (C
G3
and C
D3
) should be connected between the
OSC3/OSC4 pins and V
SS
.