MC74F259

The MC54/74F259 is a high-speed 8-bit addressable latch designed for general purpose storage applications in digital systems. MC74F259 is a multifunctional device capable of storing single line data in eight addressable latches, and also a 1-of-8 decoder and demultiplexer with active HIGH outputs. The device also incorporates an active LOW Common Clear for resetting all latches, as well as an active LOW Enable.

The MC54/74F259 has four modes of operation as shown in the Mode Select Table. In the addressable latch mode, data on the Data line (D) of MC74F259 is written into the addressed latch. The addressed latch will follow the data input with all non-addressed latches remaining in their previous states in the memory mode. All the latches remain in their previous state and are unaffected by the Data or Address inputs.

In the one-of-eight decoding or demultiplexing mode, the addressed output will follow the state of the D input with all other outputs in the LOW state. In the clear mode all outputs are LOW and unaffected by the address and data
inputs. When operating the MC54/74F259 as an addressable latch, changing more than one bit of the address could impose a transient wrong address. Therefore, this should only be done while in the memory mode. The Truth
Table below summarizes the operations of the MC54/74F259.