Casio WK-1800, Service Manual

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LCD DRIVER (LSI601: SED1278F2A)
The LCD driver can drive a dot matrix LCD having 40 segment and 16 common lines. The LSI contains 240
graphic symbols in the built-in character generator ROM, and stores 80 characters in the built-in display
data RAM. In accordance with command from the CPU, the LSI is capable of displaying up to 16 characters
simultaneously. The following table shows the pin functions of LSI 601.
Pin No. Terminal In/Out Function
1 ~ 22,
SEG1 ~ SEG40 Out Segment signal output
63 ~ 80
23 VSS — GND (0 V) source
24, 25 OSC1, OSC2 In/Out
Terminals for the built-in clock pulse generator. The external re-
sistor connected determines the oscillation frequency.
LCD drive voltage input.
26 ~ 30 V1 ~ V5 In Those voltages are used for generating the stepped pulse of the
LCD drive signals.
31, 32 LP, XSCL — Not used
33 VDD In LVDD (+5 V) source
34, 35 FR, DO — Not used
36 RS In Data/command determination terminal.High: data, Low: command
37 R/W In Read/write terminal. High: read, Low: write
Chip enable signal.
38 E In High: enable, the writing is done at fall edge.
Low: disenable
39 ~ 42 DB0 ~ DB3 — Not used. Connected to GND (0 V)
43 ~ 46 DB4 ~ DB7 In/Out Data bus
47 ~ 62 COM1 ~ COM16 Out Common signal/output
REGULATOR IC (IC202: BA9700A)
The regulator IC controls the output voltage by PWM (Pulse Wide Modulation) with outer switching transis-
tors and LC filters (integration circuit).
14
1
13
2
12
3
11
4
10
5
9
6
8
NON
INVERT
INP 1/2Vret
INVERT
INP
Vret
POWER
SW
NC VCC
7
D-TIME
CONT
Error
Amp
Vret
30k
RT CT FEED
BACK OUT NC GND
Triangle
Oscillator
PWM
Comparator
Voltage
Regulator
+ –
30k