ER-A770 (serv.man7). Internal 2 Line Display - Sharp EPOS Service Manual (repair manual). Page 3

If the level of the pin-11 signal was higher than the level of the
pin-10 (–26V being shallow), the drive time prolong. If the level of
the pin-11 signal was lower than the level of the pin-10 (–26V
being deep), the drive time shortens.

1) The pin-6 of the comparator IC4 is the overcurrent monitor input.

2) If the Q1 driving current increased and the voltage across R48

becomes above 0.6V, the comparator IC4 output turns on and its
level goes low and the voltage at 

B

 turn low.So, Q1 turns off by

the feedback circuit.

The CKDC9 is a 4-bit microcomputer developed for the POS and
provides functions to control the real-time clock, keys, and displays.
The basic functions of the CKDC9 are shown below.

Keys:

The CKDC9 is capable of controlling a maximum of 256
momentary keys. (Sharp 2-key rollover control)
Simultaneous scanning of key and switch
(When a key is scanned, the state of a mode and clerk
switch is also buffered. The host can scan the state of
switch together with the key entry data at the same time
the key is scanned.)

Switches:

Mode switch with 14 positions maximum
8-bit clerk (cashier) switch2-bit feed switch
1-bit receipt on/off switch
1-bit option switch
4-bit general-purpose switch (1-bit is used for keyboard
select)

Displays:

16-column dot display
12-column 7-segment display (column digit selectable)
All column blink controlled for the dot and 7-segment dis-
play decimal point and indicators
Programmable patterns for 7-segment display:
Four patterns
Internal driver for 7-segment display

Buzzer:

Single tone control

Clock:

Year, month, day of month, day of week, hour, minute,
second

Alarm:

Hour, minute

Interrupt request (event control):

Detection of key input, switch position change, alarm is-
sue, and counter overflow

VCC

VCC

R41
6.2k

R44
4.3k

  7

  6

1

3

12

IC4A
BA10339

R54
15k

R48
1W/0.33

  1

  4

T1

Q1
2SC3144

A

B

About

0.6V