SN54ALS259 - 8-Bit Addressable Latches

These 8-bit addressable latches are designed for general-purpose storage applications in digital systems. Specific uses include working registers, serial-holding registers, and active-high decoders or demultiplexers. They are multifunctional devices capable of storing single-line data in eight addressable latches and being a 1-of-8 decoder or demultiplexer with active-high outputs.

Four distinct modes of operation are selectable by controlling the clear () and enable (G\) inputs as shown in the function table. In the addressable-latch mode, data at the data-in terminal is written into the addressed latch. The

addressed latch follows the data input with all unaddressed latches remaining in their previous states. In the memory mode, all latches remain in their previous states and are unaffected by the data or address inputs. To eliminate the possibility of entering erroneous data in the latches, G\ should be held high (inactive) while the address lines are changing. In the 1-of-8 decoding or demultiplexing mode, the addressed output follows the level of the D input with all other outputs low. In the clear mode, all outputs are low and unaffected by the address and data inputs.

The SN54ALS259 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS259 is characterized for operation from 0°C to 70°C.

• 8-Bit Parallel-Out Storage Register Performs Serial-to-Parallel Conversion With Storage
• Asynchronous Parallel Clear
• Active-High Decoder
• Enable/Disable Input Simplifies Expansion
• Expandable for n-Bit Applications
• Four Distinct Functional Modes
• Package Options Include Plastic Small-Outline (D) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs