Reset Circuit - Citizen CLP-621 Technical Manual

(5-2) Reset circuit

This circuit performs the system reset.
When the power is turned ON, +3.3V (VCC) gradually increases from 0V. When the
voltage at pin 5 (+3.3V) of IC3 reaches a certain level, IC3 is activated and the RESET
signal changes from "Low" to "High" level. While the RESET signal is "Low", the CPU (IC1)
is reset. When the power is turned OFF and +3.3V drops below a certain level, the RESET
signal changes from "High" to "Low" level, and the CPU is reset.
The CPU outputs the GRESET signals to reset the Custom IC (IC11) and other ICs.
Power ON
+3.3V
+3.3V
0V
H
RESET
Pin 1 of IC3
L
Reset
(5-3) Clock circuit
Crystal oscillator Y1 oscillates a 16 MHz clock. This clock is send to the CPU (IC1) and the
CPU generates a 128 MHz internal clock and 64 MHz clock.
The 64MHz clock is fed to the Custom IC (IC11).
Oscillator Y2 oscillates a 48 MHz clock used for USB I/F control. It starts oscillation when
UCLKON signal (pin 77) is output from the CPU to Y2.
System Clock
(16MHz)
+3.3V
Clock for USB
UCLKON
(48MHz)
[Main PCB]
+3.3V
C3
FCX-03 (16MHz)
Y1
R2
C2 C1
Y2
Clock Generator
OUT
VDD
GND
STBY
FCXO-03 (48MHz)
P20
IC3
Voltage Detector
5 1 P17
VDD Vout
2
L : Reset
SUB
3
4
CT
GND
C4
BD5328FVE
IC1
CPU
P2
164
X1
R1
P3
165
X2
PCD1 88
UCLK
T1
159
P8
P10
UCLKON 77
PCT7
R17
2-33
2-2. Operation of Control Parts
IC1
RESET
CPU
T4
28
RESET
RESET
GRESET
23
IC11
Custom IC
26
RESET
GRESET
Bus Clock
(64MHz)
IC11
Custom IC
P132
119
CLKIN
BUSCLK
BUSCLK
Internal Clock
(128MHz)
CLP-621 & CLP-631