3-State I/O-Type Read-Back Inputs

Bus-Structured Pinout

True Logic Outputs

Package Options Include Plastic

Small-Outline (DW) Packages and Standard

Plastic (N) 300-mil DIPs

description

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 (OERB) input. When OERB is taken low, the data present at

the output of the data latches is allowed to pass back onto the input data bus. When OERB is taken high, the

output of the data latches is isolated from the D inputs. OERB 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.