3-State I/O-Type Read-Back Inputs
Bus-Structured Pinout
Choice of True or Inverting Logic
– SN74ALS666 . . . True Outputs
– SN74ALS667 . . . Inverted Outputs
Preset and Clear Inputs
Package Options Include Plastic
Small-Outline (DW) Packages and Standard
Plastic (NT) 300-mil DIPs

description
These 8-bit D-type transparent latches are
designed specifically for storing the contents of
the input data bus, plus reading back the stored
data onto the input data bus. In addition, they
provide a 3-state buffer-type output and are easily
utilized in bus-structured applications.
While the latch enable (LE) is high, the Q outputs
of the SN74ALS666 follow the data (D) inputs. The
Q outputs of the SN74ALS667 provide the inverse
of the data applied to its D inputs. The Q or
Q output of both devices is in the high-impedance
state if either output-enable (OE1 or OE2) input is
at a high logic level.
Read back is provided through the read-back
control (OERB) input. When OERB is taken low,
the data present at the output of the data latches
passes 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,
caution should be exercised to avoid a bus
conflict.
The SN74ALS666 and SN74ALS667 are
characterized for operation from 0°C to 70°C.