Texas Instruments TMS320C2XX User Manual
Page 275
NEG
Negate Accumulator
7-122
Syntax
NEG
Operands
None
Opcode
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
1
0
0
0
0
0
0
0
1
1
1
1
1
0
1
Execution
Increment PC, then ...
(ACC)
×
–1
→
ACC
Status Bits
Affected by
Affects
OVM
C and OV
Description
The content of the accumulator is replaced with its arithmetic complement (2s
complement). The OV bit is set when taking the NEG of 8000 0000h. If OVM
= 1, the accumulator content is replaced with 7FFF FFFFh. If OVM = 0, the
result is 8000 0000h. The carry bit (C) is cleared to 0 by this instruction for all
nonzero values of the accumulator, and is set to 1 if the accumulator equals
zero.
Words
1
Cycles for a Single NEG Instruction
ROM
DARAM
SARAM
External
1
1
1
1+p
Cycles for a Repeat (RPT) Execution of an NEG Instruction
ROM
DARAM
SARAM
External
n
n
n
n+p
Example 1
NEG
;(OVM = X) Convert –3544 to +3544
Before Instruction
After Instruction
ACC
X
0FFFFF228h
ACC
0
0DD8h
C
C
X
X
OV
OV
Example 2
NEG
;(OVM = 0)
Before Instruction
After Instruction
ACC
X
080000000h
ACC
0
080000000h
C
C
X
1
OV
OV
Cycles