This part is a kind of semiconductor called 87C257.

Function of this product has ADDRESS LATCHED 256K 32K x 8 UV EPROM and OTP EPROM.

Manufacturers : STMicroelectronics

Image and pinout :

Some of the text within the PDF file :

M87C257 ADDRESS LATCHED 256K (32K x 8) UV EPROM and OTP EPROM INTEGRATED ADDRESS LATCH FAST ACCESS TIME: 45ns LOW POWER “CMOS” CONSUMPTION: – Active Current 30mA – Standby Current 100µA PROGRAMMING VOLTAGE: 12.75V ELECTRONIC SIGNATURE for AUTOMATED PROGRAMMING PROGRAMMING TIMES of AROUND 3sec. (PRESTO II ALGORITHM) 28 1 FDIP28W (F) PLCC32 (C) Figure 1. Logic Diagram DESCRIPTION The M87C257 is a high speed 262,144 bit UV erasable and electrically programmable EPROM. The M87C257 incorporates latches for all address inputs to minimize chip count, reduce cost, and simplify the design of multiplexed bus systems. The Window Ceramic Frit-Seal Dual-in-Line package has a transparent lid which allows the user to expose the chip to ultraviolet light to erase the bit pattern. A new patte [ ... ]

87C257 PDF Datasheet Download