4-Bit Adder/Subtractor
Digital
·
Generic
·
Curated by CircuitSim
Details
Manufacturer
Generic
Part number
—
Pins
18
Used in
No circuits
Added
Sep 2026
About this component
Four-bit active-high arithmetic block. SUB=0 computes A+B+CIN with COUT; SUB=1 computes A−B−BIN with BOUT. Overflow reports signed two’s-complement overflow.
Parameters
Logic levels
2 parameters
VTH
Input threshold
Voltage above which arithmetic inputs are interpreted as logic high.
2.5 V
VHIGH
High output voltage
Voltage driven for an active logic-high arithmetic output.
5 V
Pins
Pins
18 pins
1
A0
Least-significant bit of operand A.
2
A1
Bit 1 of operand A.
3
A2
Bit 2 of operand A.
4
A3
Most-significant/sign bit of operand A.
5
B0
Least-significant bit of operand B.
6
B1
Bit 1 of operand B.
7
B2
Bit 2 of operand B.
8
B3
Most-significant/sign bit of operand B.
9
CIN
Active-high carry input used only when SUB is low; ignored during subtraction.
10
BIN
Active-high borrow input used only when SUB is high; ignored during addition.
11
SUB
Mode select: low adds A+B+CIN; high subtracts A-B-BIN.
12
S0
Least-significant result bit.
13
S1
Result bit 1.
14
S2
Result bit 2.
15
S3
Most-significant/sign result bit.
16
COUT
Unsigned carry output in add mode; forced low in subtract mode.
17
BOUT
Unsigned borrow output in subtract mode; forced low in add mode.
18
Overflow
Signed two’s-complement overflow for the selected operation.
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