7 OSCillaTiOn CiRCuiT anD ClOCK COnTROl
7-2
Seiko epson Corporation
S1C63003/004/008/016 TeChniCal Manual
(Rev. 1.1)
OSC3 Oscillation Circuit
7.1.4
The OSC3 oscillation circuit generates the system clock to run the CPU and some peripheral circuits at high speed.
This oscillation circuit stops when the SLP instruction is executed or the OSCC register is set to "0."
In the S1C63004/008/016, the oscillator type can be selected from ceramic, CR (external R), and CR (built-in R) by
mask option. The S1C63003 OSC3 oscillator type is fixed at CR oscillation (built-in R).
Figure 7.1.4.1 shows the configuration of the OSC3 oscillation circuit.
f
OSC3
Oscillation circuit
control signal
SLEEP status
V
SS
OSC4
OSC3
C
D3
C
G3
R
f
Ceramic
(1) Ceramic oscillation circuit – S1C63004/008/016
f
OSC3
Oscillation circuit
control signal
SLEEP status
OSC4
OSC3
R
CR
(2) CR oscillation circuit (external R) – S1C63004/008/016
R
CR
Oscillation circuit
control signal
SLEEP status
f
OSC3
(3) CR oscillation circuit (built-in R) – S1C63003/004/008/016
1.4.1 OSC3 oscillation circuit
Figure 7.
When ceramic oscillation circuit is selected, connect a ceramic resonator (Ceramic) between the OSC3 and OSC4
terminals and connecting two capacitors (C
G3
, C
D3
) between the OSC3 terminal and V
SS
, and between the OSC4
terminal and V
SS
, respectively.
When CR (external R) is selected, connect a resistor (R
CR
) between the OSC3 and OSC4 terminals.
The CR (built-in R) oscillator does not need any external elements. Leave the OSC3 and OSC4 terminals open.
1.4.1 OSC3 oscillation frequency
Table 7.
Oscillator type
Oscillation frequency
S1C63004/008/016
S1C63003
Ceramic
Typ. 4.0 MHz (3 V normal type) or
Typ. 1.0 MHz (1.5 V low-voltage type)
–
CR (external R)
Typ. 1.8 MHz (3 V normal type) or
Typ. 500 kHz (1.5 V low-voltage type)
–
CR (built-in R)
Typ. 500 kHz (3 V normal type) or
Typ. 500 kHz (1.5 V low-voltage type)
Typ. 550 kHz (3 V normal type) or
Typ. 550 kHz (1.5 V low-voltage type)
Switching the CPu Clock
7.2
Either the OSC1 clock or the OSC3 clock can be selected as the CPU system clock using the CLKCHG register.
The OSC3 oscillation circuit can be turned off (OSCC = "0") to save power while the CPU is operating with the OSC1
clock (CLKCHG = "0").
If the system needs high speed operation, turn the OSC3 oscillation circuit on (OSCC = "1") and switch over the
system clock to OSC3 (CLKCHG = "0"
→
"1").