dm93s41 Fairchild Semiconductor, dm93s41 Datasheet - Page 2

• Manufacturer Part Number: dm93s41
• Description: 4-bit Arithmetic Logic Unit
• Manufacturer: Fairchild Semiconductor

www.fairchildsemi.com
Functional Description
The DM93S41 is a 4-bit high speed parallel arithmetic logic
unit (ALU). Controlled by the four Function Select inputs
(S0–S3) and the Mode Control input (M), it can perform all
the 16 possible operations or 16 different arithmetic opera-
tions on active HIGH or active LOW operands. The Func-
tion Table below lists these operations.
When the Mode Control input (M) is HIGH, all internal car-
ries are inhibited and the device performs logic operations
on the individual bits as listed. When the Mode Control
input is LOW, the carries are enabled and the device per-
forms arithmetic operations on the two 4-bit words. The
device incorporates full internal carry lookahead and pro-
vides for either ripple carry between devices using the C
output, or for carry lookahead between packages using the
signals P (Carry Propagate) and G (Carry Generate). P
and G are not affected by carry in. When speed require-
ments are not stringent, the DM93S41 can be used in a
simple ripple carry mode by connecting the Carry output
(C
super high speed operation the Schottky DM93S41 should
be used in conjunction with the '42 carry lookahead circuit.
Function Table
H
L
Note 1: Each bit is shifted to the next more significant position
Note 2: Arithmetic operations expressed in 2s complement notation
n 4
LOW Voltage Level
HIGH Voltage Level
S3
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
) signal to the Carry input (C
Mode Select
S2
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
Inputs
S1
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
S0
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
n
) of the next unit. For
A
AB
A
Logic 1
A
B
A
A
AB
A
B
A
Logic 0
AB
AB
A
(M
B
B
B
B
B
B
Logic Arithmetic (Note 2)
H)
Active LOW Inputs
& Outputs
n 4
A minus 1
AB minus 1
AB minus 1
minus 1
A plus (A
AB plus (A
A minus B minus 1
A
A plus (A
A plus B
AB plus (A
A
A plus A (Note 1)
AB plus A
AB minus A
A
B
B
(M
2
The A
four F
equivalence over four bits when the unit is in the subtract
mode. The A
AND with the other A
more than four bits. The A
the C
The Function Table lists the arithmetic operations that are
performed without a carry in. An incoming carry adds a one
to each operation. Thus select code LHHL generates A
minus B minus 1 (2s complement notation) without a carry
in and generates A minus B when a carry is applied.
Because subtraction is actually performed by complemen-
tary addition (1s complement), a carry out means borrow;
thus a carry is generated when there is no underflow and
no carry is generated when there is underflow.
As indicated the '41 can be used with either active LOW
inputs producing active LOW outputs or with active HIGH
inputs producing active HIGH outputs. For either case the
table lists the operations that are performed to the oper-
ands labeled inside the logic symbol.
L) (C
B)
B)
n 4
B)
B)
n
outputs are HIGH and can be used to indicate logic
n
B output from the DM93S41 goes HIGH when all
signal to indicate A
L)
B output is open-collector and can be wired-
A
A
AB
Logic 0
AB
B
A
AB
A
A
B
AB
Logic 1
A
A
A
(M
B
B
B
B
B outputs to give a comparison for
B
B
Logic Arithmetic (Note 2)
H)
B signal can also be used with
Active HIGH Inputs
B and A
& Outputs
A
A
A
minus 1
A plus AB
(A B) plus AB
A minus B minus 1
AB minus 1
A plus AB
A plus B
(A
AB minus 1
A plus A (Note 1)
(A
(A
A minus 1
B
B
(M
B) plus AB
B) plus A
B) plus A
B.
L) (C
n
H)