This signifies that the
ALU-A
register entry can be crossed, Low 4 bits to High 4 bits and
vice versa, and just the low, or high, or all bits can be gated.
11 CG FIELD
CG = 0000 through 00 II
- G + 0
This signifies that the
ALU-B
register can be blocked, and that just the low, or high, or all
bits can be gated.
12 CC FIELD-CARRY INPUTS AND OUTPUTS
A. CC = 0001
- R+D+l-G
The 1 in this statement forces the carry-input line to a
1.
B. CC = 0010
- G • D-R
G
=
01001001
o
=
01000001
R- 01000001 result
The AND function (.) requires a coincidence of bits to obtain an output.
IBM Confitlenlilll
27

c.
CC
=
0011
- GQO-R
G
==
01001001
o --
01000001
R
==
01001001 result
The OR function ( n) requires a bit on either side to obtain an output.
D. CC
=
0100
The 0 in this statement forces the carry-input line to 0, and the C indicates that if a carry
out of the high-order position results, the S3 bit will be set to a
1.
E. CC
=
0110
The first C in this statement forces the value of the carry latch (S3) onto the carry-input
line. The second C indicates that
if
a carry out of the high order position results, the S3 bit
will be set to a
1.
F. CC
=
0111
- G.lfO-R
28
IBM
Confidential
G
=
01001001
o
==
0100000
J
R
=
00001000 result