MOTOROLA CMOS LOGIC DATA

MC14560B

10

Inputs

Arithmatic Expression

for R* (Result)

(N = Number of Digits,

10N = Modulus

A, B, R are Positive

Magnitudes)

Outputs

AS

“1” = Neg

BS′

“1” = Neg

Cout

“1” = Carry

(N = Number of Digits,

10N = Modulus

A, B, R are Positive

Magnitudes)

End Around

Carry (EAC)

“1” = EAC

Sign of R

“1” = Negative

Overflow

“1” = Overflow

AS

“1” = Neg

BS′

“1” = Neg

Cout

“1” = Carry

A, B, R are Positive

Magnitudes)

Carry (EAC)

“1” = EAC

Sign of R

“1” = Negative

Overflow

“1” = Overflow

0

0

0

R = A + 8

No EAC (“0”)

because R is correct

result.

Since A and B are

positive signed, R is

positive signed (“0”).

When Cout = “0”, there

is no carry (R < 10N)

and thus no overflow

(“0”).

0

0

1

When Cout = “1”, there

is a carry (R

≥ 10N)

and thus overflow

(“1”).

0

1

0

R = A – B

= A + (10N – 1 – B)

= A – B + 10N – 1

No EAC (“0”)

because 9’s

complement

expression for R is

correct result.

A

v B when Cout =

“0”; thus sign of R

must be negative

(“1”).

There is never an

overflow when

numbers of opposite

sign are added.

0

1

1

EAC = “1” because

expression for R is in

error by 1.

A > B when Cout =

“1”; thus sign of R

must be positive

(“0”).

There is never an

overflow when

1

0

0

R = B – A

= B + (10N – 1 – A)

= B – A + 10N – 1

No EAC (“0”)

because 9’s

complement

expression for R is

correct result.

B

v A when Cout =

“0”; thus sign of R

must be negative

(“1”).

overflow when

numbers of opposite

sign are added.

1

0

1

EAC = “1” because

expression for R is in

error by 1.

B > A when Cout =

“1”; thus sign of R

must be positive

(“0”).

1

1

0

R = – A – B

= (10N – 1 – A) +

(10N – 1 – B)

= – (A + B) + 2 x

10N – 2

EAC = “1” because

9’s complement

expression for R is in

error by 1.

Since A and B are

negative signed. R is

negative signed (“1”).

When Cout = “0”, there

is no Carry (R < 0N)

and (A + B) > 10N – 1

indicating overflow

(“1”).

1

1

1

10N – 2

When Cout = “1”, there

is a carry (R

≥ 10N)

and (A + B)

v 10N – 1

indicating no overflow

(“0”).

* Output of Adders

Figure 9. Truth Table Generation for EAC, Sign, and Overflow Logic