JM54AC138 Datasheet, PDF (2/10 Pages) National Semiconductor (TI) – 1-of-8 Decoder Demultiplexer

Functional Description
The ’AC/’ACT138 high-speed 1-of-8 decoder/demultiplexer
accepts three binary weighted inputs (A₀, A₁, A₂) and, when
enabled, provides eight mutually exclusive active-LOW out-
puts (O₀–O₇). The ’AC/’ACT138 features three Enable in-
puts, two active-LOW (E₁, E₂) and one active-HIGH (E₃). All
outputs will be HIGH unless E₁ and E₂ are LOW and E₃ is
HIGH. This multiple enable function allows easy parallel ex-
Truth Table
Inputs
E₁
E₂
E₃
A₀
A₁
A₂
O₀
O₁
O₂
HXXXXXHHH
XHXXXXHHH
XX L XXXHHH
pansion of the device to a 1-of-32 (5 lines to 32 lines) de-
coder with just four ’AC/’ACT138 devices and one inverter
(see Figure 1). The ’AC/’ACT138 can be used as an 8-output
demultiplexer by using one of the active LOW Enable inputs
as the data input and the other Enable inputs as strobes. The
Enable inputs which are not used must be permanently tied
to their appropriate active-HIGH or active-LOW state.
Outputs
O₃ O₄ O₅ O₆ O₇
HHHHH
HHHHH
HHHHH
L
L
H
L
L
L
L
HHHHHHH
L
L
HH
L
L
H
L
HHH
HHH
L
L
H
L
H
L
HH
L
HHHHH
L
L
HHH
L
HHH
L
H
HHH
L
L
H
L
L
HHHHH
L
HHH
L
L
HH
L
HHHHHH
L
HH
L
L
H
L
HHHHHHHH
L
H
L
L
HHHHHHHHHHH
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
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