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III PERIPHERAL BLOCK: LOW-SPEED (OSC1) OSCILLATION CIRCUIT
S1C33L03 FUNCTION PART EPSON B-III-6-1
A-1
B-III
OSC1
III-6 LOW-SPEED (OSC1) OSCILLATION CIRCUIT
Configuration of Low-Speed (OSC1) Oscillation Circuit
The Peripheral Block has a built-in low-speed (OSC1) oscillation circuit.
The low-speed (OSC1) oscillation circuit generates a 32.768-kHz (Typ.) subclock.
The OSC1 clock output by this circuit is delivered to the CLG (clock generator) in the Core Block and is used as
the source clock for the clock timer. It can also be used as a sub-clock for the low-speed (low-power) operation of
the CPU and peripheral circuits (switchable in a program).
Figure 6.1 shows the configuration of the clock system.
Clock
switch
CLKCHG
To CPU
and BCU
OSC3/PLL
clock
To peripheral
circuits
Low-speed (OSC1)
oscillation circuit
SOSC1
PF1ON
Oscillation
ON/OFF
OSC1
OSC2
I/O port Prescaler
Clock timer
FOSC1
(P14)
CLG
Figure 6.1 Configuration of Clock System
The CPU operating clock can be switched to the output (OSC1 clock) of the low-speed (OSC1) oscillation circuit
in a program. Furthermore, the oscillation circuit can be stopped in a program.
If the OSC3 clock is unnecessary such as when performing clock processing only, set the OSC1 clock for operation
of the CPU/peripheral circuits and turn off the high-speed (OSC3) oscillation circuit in order to reduce current
consumption.
The low-speed (OSC1) oscillation circuit does not stop in SLEEP mode.
For the control method when using the OSC1 clock for the operating clock of the peripheral circuits, refer to
"Prescaler".
I/O Pins of Low-Speed (OSC1) Oscillation Circuit
Table 6.1 lists the I/O pins of the low-speed (OSC1) oscillation circuit.
Table 6.1 I/O Pins of Low-Speed (OSC1) Oscillation Circuit
Pin name I/O Function
OSC1 I Low-speed (OSC1) oscillation input pin
Crystal oscillation or external clock input
OSC2 O Low-speed (OSC1) oscillation output pin
Crystal oscillation (open when external clock is used)
P14/FOSC1/DCLK I/O I/O port / Low-speed (OSC1) oscillation clock output / DCLK signal output