FINAL
Advanced
Micro
Am27C256
256 Kilobit (32,768 x 8-Bit) CMOS EPROM
Devices
DISTINCTIVE CHARACTERISTICS
■ Fast access time
■ Latch-up protected to 100 mA from –1 V to
VCC + 1 V
— 55 ns
■ High noise immunity
■ Low power consumption
■ Versatile features for simple interfacing
— 20 µA typical CMOS standby current
■ JEDEC-approved pinout
— Both CMOS and TTL input/output
compatibility
■ Single +5 V power supply
— Two line control functions
■ ±10% power supply tolerance available
■ 100% Flashrite programming
— Typical programming time of 4 seconds
■ Standard 28-pin DIP, PDIP, 32-pin TSOP and
PLCC packages
GENERAL DESCRIPTION
The Am27C256 is a 256K-bit ultraviolet erasable pro-
grammable read-only memory. It is organized as 32K
words by 8 bits per word, operates from a single +5 V
supply, has a static standby mode, and features fast sin-
gle address location programming. Products are avail-
ableinwindowedceramicDIPpackagesaswellasplas-
tic one time programmable (OTP) PDIP, TSOP, and
PLCC packages.
controls, thus eliminating bus contention in a multiple
bus microprocessor system.
AMD’s CMOS process technology provides high speed,
low power, and high noise immunity. Typical power con-
sumption is only 80 mW in active mode, and 100 µW in
standby mode.
All signals are TTL levels, including programming sig-
nals. Bit locations may be programmed singly, in blocks,
or at random. The Am27C256 supports AMD’s Flashrite
programming algorithm (100 µs pulses) resulting in typi-
cal programming time of 4 seconds.
Typically, any byte can be accessed in less than 55 ns,
allowing operation with high-performance microproces-
sors without any WAIT states. The Am27C256 offers
separate Output Enable (OE) and Chip Enable (CE)
BLOCK DIAGRAM
Data Outputs
DQ0–DQ7
V
V
V
CC
SS
PP
Output Enable
Chip Enable
and
OE
CE
Output
Buffers
Prog Logic
Y
Y
Decoder
Gating
A0–A14
Address
Inputs
262,144
Bit Cell
Matrix
X
Decoder
08007H-1
Publication# 08007 Rev. H Amendment/0
Issue Date: May 1995
2-32