GENERAL DESCRIPTION
The Am27C256 is a 256K-bit ultraviolet erasable programmable 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 single address location programming. Products are available in windowed ceramic DIP packages as well as plastic one time programmable (OTP) PDIP, TSOP, and PLCC packages.
Typically, any byte can be accessed in less than 55 ns, allowing operation with high-performance microprocessors without any WAIT states. The Am27C256 offers separate Output Enable (OE) and Chip Enable (CE) 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 consumption is only 80 mW in active mode, and 100 µW in standby mode.
All signals are TTL levels, including programming signals. Bit locations may be programmed singly, in blocks, or at random. The Am27C256 supports AMD’s Flashrite programming algorithm (100 µs pulses) resulting in typical programming time of 4 seconds.

DISTINCTIVE CHARACTERISTICS
■ Fast access time
   — 55 ns
■ Low power consumption
   — 20 µA typical CMOS standby current
■ JEDEC-approved pinout
■ Single +5 V power supply
■ ±10% power supply tolerance available
■ 100% Flashrite programming
   — Typical programming time of 4 seconds
■ Latch-up protected to 100 mA from –1 V to VCC + 1 V
■ High noise immunity
■ Versatile features for simple interfacing
   — Both CMOS and TTL input/output compatibility
   — Two line control functions
■ Standard 28-pin DIP, PDIP, 32-pin TSOP and PLCC packages