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

description

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 (CLR) 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.