MOTOROLA CMOS LOGIC DATA
6–439
MC14560B
Table 1. Sum = A + B + C
Binary Sums
Decimal
Numbers
Corrected
Binary Sums
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
Non valid
1101
BCD
1110
representation
1111
0000 + Carry
0001 + Carry
0010 + Carry
0011 + Carry
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
0000 + Carry
0001 + Carry
0010 + Carry
0011 + Carry
0100 + Carry
0101 + Carry
0110 + Carry
0111 + Carry
1000 + Carry
1001 + Carry
ADDITION AND SUBTRACTION OF SIGNED NBCD
NUMBERS
Using MC14560 NBCD Adders and MC14561 9’s Comple-
menters, a sign and magnitude adder/subtracter can be con-
figured (Figure 5). Inputs A and B are signed positive (AS, BS
= “0”) or negative (AS, BS = “1”). B is added to or subtracted
from A under control of an Add/Sub line (subtraction = “1”).
The result, R, of the operation is positive signed, positive
signed with overflow, negative signed, or negative signed
with overflow. Add/subtract time is typically 0.6 + 0.4n
µ
s for
n decades.
An exclusive–OR of Add/Sub line and BS produces B
′
,
which controls the B complementers. If BS, the sign of B, is a
logical “1” (B is negative) and the Add/Sub line is a “0” (add
B to A), then the output of the exclusive–OR (BS
′
) is a logical
“1” and B is complemented. If BS = “1” and Add/Sub = “1”, B
is not complemented since subtracting a negative number is
the same as adding a positive number. When Add/Sub is a
“1” and BS = “0”, BS
′
is a “1” and B is complemented. The A
complementer is controlled by the A sign bit, AS. When AS =
“1”, A is complemented.
Figure 4. Unsigned NBCD Addition Algorithm
6,941
5,870
+
4 BIT BINARY FULL ADDER
DIGIT BINARY SUMS
BINARY SUMS WITH
CARRY FROM CONVERTERS
CODE CONVERTERS
CORRECTED SUM
12,811
A
B
Cin
Cout
BINARY TO NBCD
CODE CONVERTER
RESULT, R
A1
B1
A2
B2
An
Bn
Cin
Cin
Cin
Cout
Cout
Cout
R1
R2
Rn
OVERFLOW
THOUSANDS
0110
0101
HUNDREDS
1001
1000
TENS
0100
0111
UNITS
0001
0000
ADDER
Cin
ADDER
Cin
ADDER
Cin
ADDER
1
1
0
1011
0001
1011
0001
1
1100
0010
1011
0001
1
Cout
Cout
Cout
Cout
1
0 0 1 0
1 0 0 0
0 0 0 1
0 0 0 1
Figure 5. Addition of Unsigned NBCD Numbers
(a) MC14560 Block Diagram
(b) n–Decade Adder
Typical Add Time = 0.1 + 0.2n
µ
s
where n = Number of Decades
4 BIT BINARY ADDERS
MC14560
MC14560
MC14560
Summary of Contents for CMOS Logic
Page 1: ......
Page 5: ...iv MOTOROLA CMOS LOGIC DATA ...
Page 6: ...Master Index 1 ...
Page 12: ...Product Selection Guide 2 ...
Page 17: ...The Better Program 3 ...
Page 20: ...B and UB Series Family Data 4 ...
Page 25: ...CMOS Handling and Design Guidelines 5 ...
Page 32: ...CMOS Handling and Design Guidelines 5 ...
Page 39: ...Data Sheets 6 ...
Page 234: ...MOTOROLA CMOS LOGIC DATA MC14174B 6 196 FUNCTIONAL BLOCK DIAGRAM TIMING DIAGRAM ...
Page 238: ...MOTOROLA CMOS LOGIC DATA MC14175B 6 200 FUNCTIONAL BLOCK DIAGRAM TIMING DIAGRAM ...
Page 555: ...CMOS Reliability 7 ...
Page 561: ...Equivalent Gate Count 8 ...
Page 563: ...Packaging Information Including Surface Mounts 9 ...
Page 571: ......