15
15 – 24
ALU
SUBTRACT X-Y / SUBTRACT X-Y with BORROW
AC Set if a carry is generated. Cleared otherwise.
Instruction Format:
Conditional ALU/MAC operation, Instruction type 9:
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 1 0 0 Z AMF Yop Xop 0 0 0 0 COND
AMF specifies the ALU or MAC operation. In this case,
AMF = 10110 for xop – yop + C – 1 operation.
AMF = 10111 for xop – yop operation.
Note that xop + C – 1 is a special case of xop – yop + C – 1 with yop=0.
Z: Destination register Yop: Y operand
Xop: X operand COND: condition
(xop – constant) Conditional ALU/MAC operation, Instruction Type 9:
(ADSP-217x, ADSP-218x, ADSP-21msp58/59 only)
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 1 0 0 Z AMF YY Xop CC BO COND
AMF specifies the ALU or MAC operation, in this case:
AMF = 10110 for xop – constant + C – 1
AMF = 10111 for xop – constant
Z: Destination register COND: condition
Xop: X operand
BO, CC, and YY specify the constant (see Appendix A, Instruction Coding).
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