Epson LQ-2550 Technical Manual page 257

A.1.1.3 27512
The 27512 is an EPROM,
Features:
65536 words X 8 bits
TTL compatible input/output
Acccess time: 200 ns (max.)
28 pins (DIP)
Terminal Functions:
AO to Al 5: Address input
Output enable input/programming power supply
00 to 07: Data output
Power supply (+5 V)
Mode
Read
Output disable
Standby
Program
Program inhibit
P r o g r a m v e r i f y
* : Vn-1 o r VIL
which is an ultra-violet erasable and electrically programmable
Vet
Circuit
I
6
Column
Decoder
A
Z
I
A4
10
Row
Buffer Decoder
Figure A-1 1. 27512 Block Diagram
Table A-4. 27512 Signal Status
Vcc
(28) (22)
L
I
5V
I
*
6 V
VPP
L
Figure A-10. 27512 Pin
02 04
? ? ? ? ? ?
Output Buffer
I
Column Gate
1 0 2 4
0 0 -
(20) (1 1 - 13, 15 - 19)
L Data output
*
High impedance
H
L Data input
H H i g h i m p e d a n c e
L D a t a o u t p u t
A-1 2
28 Va
27
4
2 5 Aa
24 At
23 A
I I
7
2 2
8 2 1 AM
20 E
19 al
10
00 11
17 0s
01
15 03
Diagram
01
7 ?
0 7
Power
Active
Standby
—
A c t i v e
# -
ROM. ';
'
.