The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. 74LS640 octal bus transceivers are designed for asynchronous two-way communication between data buses The devices transmit data from the A bus to the B bus or from the B bus to the A bus depending upon the level at the direction control (DIR) input

74LS640 Features
- Designed for Asynchronous two-way Communication between Data Buses
- Enable Input for Disabling the Device
- 3-State Outputs Drive Bus Lines Directly
- Operating Temperature up to 70°C
- Standard TTL Switching Voltages
74LS640 Specifications
Supply Voltage | 4.75 – 5.25Vdc |
Maximum Clock Frequency | 40Mhz |
Power Dissipation | 2mW/gate @100kHz |
Minimum Output Current | 8mA |
Propagation Delay | 10nS |
Fan Out (TTL Loads) | 20 |
74LS640 Pinout Diagram

74LS640 Pin Description
Pin No | Pin Name | Description |
1 | T/R’ | Control Pin |
2 | A0 | Input / Output Of Bus Transceiver A |
3 | A1 | Input / Output Of Bus Transceiver A |
4 | A2 | Input / Output Of Bus Transceiver A |
5 | A3 | Input / Output Of Bus Transceiver A |
6 | A4 | Input / Output Of Bus Transceiver A |
7 | A5 | Input / Output Of Bus Transceiver A |
8 | A6 | Input / Output Of Bus Transceiver A |
9 | A7 | Input / Output Of Bus Transceiver A |
10 | GND | Ground |
11 | B7 | Input / Output Of Bus Transceiver B |
12 | B6 | Input / Output Of Bus Transceiver B |
13 | B5 | Input / Output Of Bus Transceiver B |
14 | B4 | Input / Output Of Bus Transceiver B |
15 | B3 | Input / Output Of Bus Transceiver B |
16 | B2 | Input / Output Of Bus Transceiver B |
17 | B1 | Input / Output Of Bus Transceiver B |
18 | B0 | Input / Output Of Bus Transceiver B |
19 | OE’ | Enable Pin 2 |
20 | VCC | Positive Supply |
Applications
- Provide bidirectional, input or output control, of either digital or analogue devices to a common shared data bus
74LS640 Alternative Equivalent
74LS645
Download 74LS640 Octal Inverting Bus Transceiver Tri-State Datasheet from the link given below.