Sharp ER-A750 Service Manual page 54

2-10. CKDC7 (HD404728A91FS)
1) General description
The CKDC7 is a 4-bit microcomputer developed for the ER-A750 and
provides functions to control the real-time clock, keys, and displays.
The basic functions of the CKDC7 are shown below.
Keys: The CKDC7 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
2) Pin description
Pin Signal
Symbol In/Out
No. name
1 SB SB Out
2 SC SC Out
3 SD SD Out
4 SE SE Out
5 SF SF Out
6 SG SG Out
7 P4 COM/AP Out
8 P0 NC —
9 P1 NC —
10 P2 DP Out
11 P3 ID Out
12 MODR VCC —
13 CFSR CFSR In
14 KEX0 KEX0 Out
15 KEX1 KEX1 Out
16 RQ GND —
17 SKR0 VCC —
18 ST0 ST0 Out
19 ST1 ST1 Out
20 ST2 ST2 Out
21 ST3 ST3 Out
22 POFF POFF In
23 STOP STOP In
Function
Segment B
Segment C
Segment D
Segment E
Segment F
Segment G
NC
NC
Decimal point
Indicator
+5V
Clerk key, Feed key, Switch
return signal
Key exchange signal
Key exchange signal
GND
+5V
Key strobe signal
Key strobe signal
Key strobe signal
Key strobe signal
Power off signal
STOP signal
Pin Signal
Symbol
No. name
24 DDIG VCC
25 DCS NC
26 VCC VCC
27 SCK SCK
28 HTS HTS
29 STH STH
30 SDISP GND
31 BUZZ BUZZ
32 DSCK NC
33 SRES RESET
34 DS0 NC
35 SHEN SHEN
36 IRQ IRQ
37 KR0 KR0
38 KR1 KR1
39 KR2 KR2
40 KR3 KR3
41 RESET CKDCR
42 OSC2 OSC2
43 OSC1 OSC1
44 GND GND
45 CL1 CL1
46 CL2 CL2
47 TEST VCC
48 G0 G0
49 G1 G1
50 G2 G2
51 G3 G3
52 G4 G4
53 G5 G5
54 G6 G6
55 G7 G7
56 G8 G8
57 G9 G9
58 G10 G10
59 G11 G11
60 PO0 NC
61 PO1 NC
62 PO2 NC
63 PO3 NC
64 SA SA
7 – 24
In/Out Function
— +5V
— NC
— +5V
In Clock signal
In Key data from host
Out Key data to host
— GND
Out Buzzer
— NC
Out Reset signal
— NC
Out Shift enable signal
Out Key request signal
In Key return signal
In Key return signal
In Key return signal
In Key return signal
In CKDC reset signal
— Clock
— Clock
— GND
— Time clock
— Time clock
— +5V
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
Out Display digit signal
NC
NC
— NC
— NC
— Segment A