General Description
The 27C256 is a high-speed 256K UV erasable and electrically
reprogrammable CMOS EPROM, ideally suited for applications
where fast turnaround, pattern experimentation
and low power consumption are important requirements.
The 27C256 is designed to operate with a single a5V power
supply with g10% tolerance. The CMOS design allows
the part to operate over Military Temperature Range.
The 27C256 is packaged in a 28-pin dual-in-line package
with transparent lid and a 32-pin windowed LCC. The transparent
lid allows the user to expose the chip to ultraviolet
light to erase the bit pattern. A new pattern can then be
written electrically into the device by following the programming
procedure.
This EPROM is fabricated with National's proprietary, time
proven CMOS double-poly silicon gate technology which
combines high performance and high density with low power
consumption and excellent reliability.
The 27C256 specified on this data sheet is fully compliant
with MIL-STD-883, Revision C.

Features
Y Clocked sense amps for fast access time down to
250 ns
Y Low CMOS power consumption
Ð Active power: 55 mW max
Ð Standby power: 0.55 mW max
Y Performance compatible to NSC800TM CMOS
microprocessor
Y Single 5V power supply
Y Pin compatible with NMOS 256K EPROMs
Y Fast and reliable programming (0.5 ms for most bytes)
Y Static operationÐno clocks required
Y TTL, CMOS compatible inputs/outputs
Y TRI-STATEÉ output
Y Optimum EPROM for total CMOS systems
Y Windowed DIP and LCC package options
Y Specifications guaranteed over full military temperature
range (b55§C to a125§C)
Y This device is processed in compliance with SMD
86063, and the DIP version is dual marked