Octal D-Type Transparent Read-Back Latches

This 8-bit latch is designed specifically for storing the contents of the input data bus and providing the capability of reading back the stored data onto the input data bus.

The eight latches are transparent D-type latches. While the latch-enable (LE) input is high, the Q outputs follow the data (D) inputs.

Read back is provided through the output-enable () input. When is taken low, the data present at the output of the data latches is allowed to pass back onto the input data bus. When is taken high, the output of the data latches is isolated from the D inputs. does not affect the internal operation of the latches; however, precautions should be taken not to create a bus conflict.

The SN74ALS990 is characterized for operation from 0°C to 70°C.