You are buying one HM62256BLP-7 70 ns HITACHI SRAM 5V 256K-bit 32K x 8 28-Pin PDIP. 

Description
The Hitachi HM62256B Series is a CMOS static RAM organized 32,768-word × 8-bit. It realizes higher
performance and low power consumption by employing 0.8
µm Hi-CMOS process technology. The
device, packaged in 8
× 14 mm TSOP, 8 × 13.4 mm TSOP with thickness of 1.2 mm, 450 mil SOP (foot
print pitch width), 600 mil plastic DIP, or 300 mil plastic DIP, is available for high density mounting. It
offers low power standby power dissipation; therefore, it is suitable for battery backup systems.

Features

Single 5.0 V supply: 5.0 V ± 10%
Access time: 70 ns (max)
Power dissipation:
Active: 25 mW (typ) (f = 1 MHz)
Standby: 1.0 µW (typ)
Completely static memory
No clock or timing strobe required
Equal access and cycle times
Common data input and output
Three state output
Directly TTL compatible all inputs and outputs
Battery backup operation