mc14560b Freescale Semiconductor, Inc, mc14560b Datasheet - Page 10

• Manufacturer Part Number: mc14560b
• Description: Nbcd Adder
• Manufacturer: Freescale Semiconductor, Inc

* Output of Adders
“1” = Neg
“1” = Neg
MC14560B
10
A S
A S
0
0
0
0
1
1
1
1
“1” = Neg
“1” = Neg
Inputs
B S
B S
0
0
1
1
0
0
1
1
“1” = Carry
“1” = Carry
Figure 9. Truth Table Generation for EAC, Sign, and Overflow Logic
C out
C out
0
1
0
1
0
1
0
1
R = A + 8
R = A – B
R = B – A
R = – A – B
Arithmatic Expression
(N = Number of Digits,
(N = Number of Digits,
A, B, R are Positive
A, B, R are Positive
A, B, R are Positive
= A + (10 N – 1 – B)
= A – B + 10 N – 1
= B + (10 N – 1 – A)
= B – A + 10 N – 1
= (10 N – 1 – A) +
= – (A + B) + 2 x
10 N = Modulus
10 N = Modulus
for R* (Result)
(10 N – 1 – B)
10 N – 2
10 N – 2
Magnitudes)
Magnitudes)
Magnitudes)
No EAC (“0”)
because R is correct
result.
No EAC (“0”)
because 9’s
complement
expression for R is
correct result.
EAC = “1” because
expression for R is in
error by 1.
No EAC (“0”)
because 9’s
complement
expression for R is
correct result.
EAC = “1” because
expression for R is in
error by 1.
EAC = “1” because
9’s complement
expression for R is in
error by 1.
End Around
Carry (EAC)
Carry (EAC)
“1” = EAC
“1” = EAC
Since A and B are
positive signed, R is
positive signed (“0”).
A
“0”; thus sign of R
must be negative
(“1”).
A > B when C out =
“1”; thus sign of R
must be positive
(“0”).
B
“0”; thus sign of R
must be negative
(“1”).
B > A when C out =
“1”; thus sign of R
must be positive
(“0”).
Since A and B are
negative signed. R is
negative signed (“1”).
v
v
“1” = Negative
“1” = Negative
B when C out =
A when C out =
Sign of R
Sign of R
Outputs
MOTOROLA CMOS LOGIC DATA
When C out = “0”, there
is no carry (R < 10 N )
and thus no overflow
(“0”).
When C out = “1”, there
is a carry (R
and thus overflow
(“1”).
There is never an
There is never an
overflow when
overflow when
overflow when
numbers of opposite
numbers of opposite
sign are added.
sign are added.
When C out = “0”, there
is no Carry (R < 0 N )
and (A + B) > 10 N – 1
indicating overflow
(“1”).
When C out = “1”, there
is a carry (R
and (A + B)
indicating no overflow
(“0”).
“1” = Overflow
“1” = Overflow
Overflow
Overflow
v
10 N )
10 N )
10 N – 1