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THE 2920 SIGNAL PROCESSOR
Table 3-5. Memory-ALU Instruction Opcodes
a.
Non-Conditional Arithmetic
ALU
MNEM
Operation*
210
000
XOR
BED(A· 2k) .... B
001
AND
BA(A·2 k ) .... B
010
LIM
+ 1 ** .... B if A
~
0
-1
.... Bif A<O
o
1 1
ABS
0+
I
A·2 k
I ....
B
I 0 0
ABA
B+
I
A·2 k
I ....
B
I 0 1
SUB
B- (A·2 k ) .... B
I 1 0
ADD
B+ (A·2 k ) .... B
I 1 1
LDA
0+ (A·2 k ) .... B
*Note-k is the value selected by the shift code, -13
~
k
~
+ 2
* *Note-the largest positive value (1-2-
24 )
is stored.
b.
Conditional Arithmetic Operations
Description/Comments
Sign of A saturates output
Absolute Value
Absolute Value and Add
ALU Functions made Conditional by selected codes in the Analog Control Field.
ALU Function
Bit Tested
IF Tested Bit
=
0
IF Tested Bit
=
1
ADD (110)
DAR (n)
NO-OP(B+O .... B)
ADD (B+A· 2 k .... B)
LDA(lll)
DAR (n)
NO-OP(B+O .... B)
LDA (O+A· 2 k .... B)
SUB
(101)
PREV cy
ADD(B+A·2 k .... B)
SUB (B-A· 2k .... B)
cy .... DAR(n)
cy .... DAR(n)
Note- DAR(n) represents a bit of the DAR, as selected by the conditional operand in the analog control field. For ADD and
LDA, the selected bit is tested. For SUB, the selected bit is altered by being set to the carry output of the highest order
position of the ALU; and the conditional operation is base,d on a test of the carry resulting from the previous ALU
operation. For SUB with CNDS, CY is set to the DAR.
c.
Overflow Manipulation Operations
ALU Function
ABA
XOR
"Don't Care"
AD Function
CND(K)
CND(K)
EOP
3-8
Description
Disable Overflow
Enable Overflow
Enable Overflow
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