The MM74HC646N is an Octal Transceiver/Register with 3-STATE Outputs manufactured by National Semiconductor (now Texas Instruments). It features eight bidirectional transceivers (A and B ports) that can either transmit data from A to B, B to A, or isolate the two ports. It also includes an internal register that can store data being transmitted. The 3-STATE outputs allow for bus isolation when the device is not actively transmitting data.

Applications

• Microprocessor Systems
• Memory Interface
• Bidirectional Data Buffering
• Data Bus Isolation
• Peripheral Interfacing

Features

• High Speed: Typical propagation delay of 15 ns
• Bidirectional Data Flow: Allows data transmission in both directions
• 3-STATE Outputs: Provides high impedance state for bus isolation
• Internal Register: Stores data being transmitted
• TTL Compatible Inputs: Directly interfaces with TTL logic

Benefits

• Increased System Performance: High-speed operation reduces delays in data transfer
• Simplified System Design: Bidirectional capability reduces component count
• Enhanced Bus Management: 3-STATE outputs prevent bus contention
• Provides temporary data storage
• Easy Integration: TTL compatible inputs simplify interfacing with other logic devices

Additional Details

The MM74HC646N is housed in a DIP (Dual In-line Package). Several control inputs determine the operating mode. The direction control (DIR) input selects the direction of data flow. Output enable pins (/OE) control the 3-STATE outputs. The clock (CLK) input latches data into the internal register. This device is suitable for applications requiring bidirectional data transfer with temporary storage and bus isolation capabilities.