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
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.
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