Epson PX-8 - Clock Generator Circuit

REV.-A
2.4 Clock Generator Circuit
There are three clock oscillator circuits listed in Table 2-9 on the MAPLE board. Two clock pulse
signals
of these three are fed to the IC 6A, which divides and distributes them to the LSls listed in
the table. The remaining signal is generated by a CR oscillator circuit and used as the switching
signal for the DC-DC converters which generate special voltages.
Table 2-9 Clock Oscillator Circuits
Oscillator Circuit Primary Frequency
Output Frequency and
Signal Destination
Main
oscillator circuit (CR1)
9.8304 MHz
4.9
MHz ~ 7C
Clock
oscillator circuit (CR2)
32.768 kHz
1.0 kHz
~ 2E
Voltage regulator
oscillator
35 kHz
35 kHz ~ RS-232C, (± 8V)
circuit
~ LCD regulator (-1 5V)
5V regulator (+5V)
2.4.1. CR1
Oscillator Circuit
The CR1 oscillator circuit starts functioning when power is turned on. The output is amplified by
IC 7B and is then fed to IC 6A. This IC consists of two frequency divider circuits and the primary
frequency is halved and quartered to produce two clock signals of 4.9 MHz and 2.45 MHz.
CR1 9.8304 MHz
6A(GAH40D)
0
4.9152 MHz
R137 R134
10M
10M
2.4576 MHz
-7-2
-7-2
6 5
10P
78
10P
IC20 IC21
Fig.2-48 CR1 Oscillator Circuit
2-50