SN7489

The SN7489 has the following features including For Application as a"Scratch Pad" Memory with Nondestructive Read-Out;Fully Decoded Memory Organized as 16 Words of Four Bits Each;Fast Access Time.33 ns Typical;Diode-Clamped, Buffered Inputs;Open-Collector Outputs Provide Wire-AND Capability;Typical Power Dissipation.375 mW;Compatible with Most TTL Circuits.

This  64-bit  active-element  memory  is  a monolithic, high-speed, transistor-transistor logic(TTL) array of 64 flip-flop memory cells organized in a matrix to provide 16 words of four bits each Each of the 16 words is addressed in straight binary with full on-chip decoding.The buffered memory inputs consist of four address lines, four data inputs, a write enable and a memory enable for controlling the entry and access of data. The memory has opencollector  outputs  which  may  be  wired-AND connected to permit expansion up 20 4/V4 words of N-bit length without additional output buffering. Access  time  is  typically  33 nanoseconds; power dissipation is typically 375 milliwatts.Information present at the data inputs is written into the memory by addressing the desired word and holding both the memory enable and write enable low.Since the internal output of the data input gate is common to the input of the sense amplifier, the sense output will assume the opposite state of the information at the data inputs when the write enable is low.

The complement of the information which has been written into the memory is nondestructiveYy read out at the four sense outputs. This is accomplished by holding the memory enable low, the write enable high, and selecting the desired address.The products described in this document are designed, developed and manufactured as contemplated for general use, including without limitation, ordinary industrial use, general office use, personal use, and household use, but are not designed, developed and manufactured as contemplated (1) for any use that includes fatal risks or dangers that, unless extremely high safety is secured, could have a serious effect to the public, and could lead directly to death, personal injury, severe physical damage or other loss.