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.