Osc1 Oscillator Circuit - Epson S1C17001 Technical Manual

7 OSCILLATOR CIRCUIT (OSC)

7.3 OSC1 Oscillator Circuit

The OSC1 oscillator circuit generates a (typ.) 32.768 kHz sub-clock.
The OSC1 clock is generally used as the timer operation clock (for the clock timer, stopwatch timer, watchdog tim-
er, and 8-bit OSC1 timer). It reduces power consumption and can be used as the system clock instead of the OSC3
clock when no high-speed processing is required.
The oscillator circuit is crystal-based. The oscillator circuit also allows use of an external clock input.
Figure 7.3.1 illustrates the OSC1 oscillator circuit configuration.
C
G1
OSC1
R
X'tal1 f
R
d
C
D1 OSC2
V
SS
(1) Crystal oscillator circuit
When this is used as a crystal oscillator circuit, connect a crystal oscillator X'tal1 (typ. 32.768 kHz) and feedback
resistor (R ) between the OSC1 and OSC2 pins. Connect two capacitors (C
f
pins and V . A drain resistor (R
SS
When used with external clock (max. 100 kHz) input, the OSC2 pin should be left free, and a clock with a duty ra-
tio of 50% at LV level should be input to the OSC1 pin.
DD
If the OSC1 oscillator circuit is not used, connect the OSC1 pin to V
OSC1 oscillation on/off
The OSC1 oscillator circuit stops oscillating if OSC1EN (D1/OSC_CTL register) is set to 0 and starts oscillat-
ing if set to 1. The OSC1 oscillator circuit stops oscillating even in SLEEP mode.
∗ OSC1EN: OSC1 Enable Bit in the Oscillation Control (OSC_CTL) Register (D1/0x5061)
Stabilization wait time at start of OSC1 oscillation
The OSC1 oscillator circuit incorporates an oscillation stabilization wait timer to prevent malfunctions due
to unstable clock operations at the start of OSC1 oscillation—for example, when power is first turned on, on
awaking from SLEEP, or when the OSC1 oscillation circuit is turned on via software. The OSC1 clock does not
feed the system for a period of 256 cycles after the start of oscillation.
58
OSC1
Oscillator circuit
control signal
SLEEP control
OSC1
OSC2
V
SS
(3) When not used
Figure 7.3.1: OSC1 oscillator circuit
) should be connected between the OSC2 pin and C
d
EPSON
OSC1
LV
DD
V
SS
External
clock
N.C.
OSC2
(2) External clock input
Low level
Oscillator circuit
control signal
SLEEP control
and C
G1
D1
while leaving the OSC2 pin open.
SS
OSC1
Oscillator circuit
control signal
SLEEP control
) between the OSC1/OSC2
D1
, if required.
S1C17001 TECHNICAL MANUAL