ER-A880 (serv.man5). ERA8DP One Line Display Service Manual - Sharp EPOS Service Manual (repair manual). Page 3

1) The pin-4 of the comparator IC1B is the overcurrent monitor input.

2) If the Q1 driving current increased and the voltage across R1

becomes above 0.5V, the comparator IC1B output turns on and its
level goes low and the voltage at 

B

 turn low.So, Q1 turns off by

the feedback circuit.

The CKDC4 is a 4-bit microcomputer developed for the ECR and
provides functions to control the real-time clock, keys, and displays.
The basic functions of the CKDC4 are shown below.

Keys:

The CKDC4 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) switch
2-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
display 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

Alarm:

Hour, minute

Interrupt request (event control):

Detection of key input, switch position change, alarm
issue, and counter overflow

Fig. 2-5

IC1B
IR2339N

Q1
C3144

5

4

1

B

R1
0.39/1W

About 0.5V

R103
4.3K

3

A

VCC
(+5V)

R102
6.2K

R108
1.1K

IRQ
SHEN
STH
HTS
SCK
POFF
STOP
SRES

CKDCR

HOST
SYSTEM

7SEG-DISPLAY 12DIG

DOT-DISPLAY 16DIG

GO

~

G

1

1

SA

~

S

G

P0

,1

,4

CKDC 4

P2,3

DI

G0

0

DI

G1

5

SE

G

0

0

SE

G

1

5

DOT DISP CONT.
M66004EP

SRES,DCS,DSCK,DSO

ST0~3

KEX0,1

DECODER
LS138

DECODER
LS138

KEYBOARD
MAX. 244key

DECODER
LS153

DECODER
LS153

D

ISPS

L

SKR

O

Q

BUZZ

BUZZER

CSFR
MODR

KR0

~

3

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