RCA Spectra 70 - Page 143

Add Word
(AR) (A)
General Description
Format
(RR)
(RX)
Condition Code
Interrupt
Action
Notes
Fixed-Point
I nstruction8
• The operands specified by the first and second addresses (R
1
and
R2 or X
2
/B
2
/D
2
)
are added and the sum is placed in the general register
specified by the first address (R]). The magnitude and the sign of the
sum determine the condition code setting.
I
(AR) 1A
Rl
R2
0 7
8
11 12
I (A)
5A
R
.
X
2
0
7 8 11
12
• 0 - sum is zero.
1 -
sum is less than zero.
2 -
sum is greater than zero.
3 - overflow.
• Fixed-point overflow.
Address
error:
Addressing (RX format).
Specification (RX format).
15
B2
15 16
19
20
31
• 1. All 32 bits of both operands participate in the addition. If the carries
into and out of the sign bit disagree, an overflow exists. The overflow
does
not alter the sign bit created by the carries.
2. A negative overflow results in a positive sum and a positive overflow
results in a negative sum with overflow bits being lost.
3. A zero
result is always positive.
4.
The operand specified by the second address is unaltered.
l34