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.