The MM74189N is a 64-Bit Random Access Memory (RAM) organized as 16 words by 4 bits. It was manufactured by National Semiconductor, which is now part of Texas Instruments (TI). This RAM IC is designed for use in small memory applications and digital logic systems where a small, fast memory is required. It features open-collector outputs for easy memory expansion.

Applications

• Scratchpad memory
• Control store memory
• Buffer memory
• Look-up tables
• Small data storage applications

Features

• Organization: 16 words x 4 bits
• Open-collector outputs: Allows for easy memory expansion by wiring multiple chips together.
• TTL compatibility: Compatible with standard TTL logic levels.
• Address inputs: 4 address lines to select one of the 16 memory locations.
• Write enable input: Controls the writing of data into the memory.

Benefits

• Small memory size: Suitable for applications where a small amount of fast memory is needed.
• Easy memory expansion: Open-collector outputs simplify the expansion of memory capacity.
• TTL compatible: Easy to interface with other digital logic circuits.
• Simple operation: Straightforward read and write operations make it easy to use.
• Cost-effective: Provides a low-cost solution for small memory requirements.

Additional Details

The MM74189N is typically available in a 16-pin DIP (Dual In-line Package). The open-collector outputs require external pull-up resistors for proper operation. This RAM requires a 5V power supply. While this part is now considered obsolete, it was a crucial component in early digital systems, providing a small and fast memory solution. The memory can be written to and read from using the address lines, write enable input, and data input/output lines.