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.