Hammond X-5 - 8-Bit Encoder; Truth Table

8-BIT ENCODER
TRUTH TABLE
INPUT
OUTPUT
D7 D6 D5 D4 D3 D2
01
DO QS Q2
HI
QO
EO
X
X
X X X X
X
X
1 1
1
1
X X X X X
X X 1 1 1
1 1 X X
X X
X X 1 1
1 1 X
X
X X X 1 1
1 1 X X
X X 1
1
1
X X X 1
1
1
•
1
X X I
1 I
X 1
V1 1
1
X'
Don't Care Logicl
=
High LogicO-Low
D7 is
the
highest priority
and
DO is
the lowest The priority encoder is inhibited when
the
chip-enable input
E|
is low. When
E| is high,
the binary representation of the hkjhest
priority input
appears on output lines
0.2-0.0, and the group select line
OS
is high to
indicate
that priority inputs are present. The enable-out
(Ed)
is high when
no
priority
inputs are
present.