FINAL
Publication# 12082 Rev: F Amendment/0
Issue Date: May 1998
Am27X256
256 Kilobit (32 K x 8-Bit) CMOS ExpressROM Device
DISTINCTIVE CHARACTERISTICS
a73 As an OTP EPROM alternative:
— Factory optimized programming
— Fully tested and guaranteed
a73 As a Mask ROM alternative:
— Shorter leadtime
— Lower volume per code
a73 Fast access time
— 55 ns
a73 Single +5 V power supply
a73 Compatible with JEDEC-approved EPROM
pinout
a73 ±10% power supply tolerance
a73 High noise immunity
a73 Low power dissipation
— 20 µA maximum CMOS standby current
a73 Available in Plastic Dual-In-line Package (PDIP)
and Plastic Leaded Chip Carrier (PLCC)
a73 Latch-up protected to 100 mA from –1 V to
V
CC
+ 1 V
a73 Versatile features for simple interfacing
— Both CMOS and TTL input/output compatibility
— Two line control functions
GENERAL DESCRIPTION
The Am27X256 is a factory programmed and tested
OTP EPROM. It is programmed after packaging prior to
final test. Every device is rigorously tested under AC
and DC operating conditions to your stable code. It is
organized as 32 Kwords by 8 bits per word and is avail-
able in plastic dual in-line packages (PDIP), as well as
plastic leaded chip carrier (PLCC) packages. Express-
ROM devices provide a board-ready memory solution
for medium to high volume codes with short leadtimes.
This offers manufacturers a cost-effective and flexible
alternative to OTP EPROMs and mask programmed
ROMs.
Data can be accessed as fast as 55 ns, allowing
high-performance microprocessors to operate with re-
duced WAIT states. The device offers separate Output
Enable (OE#) and Chip Enable (CE#) controls, thus
eliminating bus contention in a multiple bus micropro-
cessor system.
AMD’s CMOS process technology provides high
speed, low power, and high noise immunity. Typical
power consumption is only 80 mW in active mode, and
100 µW in standby mode.
BLOCK DIAGRAM
12082F-1
A0–A14
Address
Inputs
CE#
OE#
V
CC
V
SS
Data Outputs DQ0–DQ7
Output
Buffers
Y
Gating
262,144
Bit Cell
Matrix
X
Decoder
Y
Decoder
Output Enable
Chip Enable
and
Prog Logic