Spac – Texas Instruments TMS320C2XX User Manual
Page 313
SPAC
Subtract PREG From Accumulator
7-160
Syntax
SPAC
Operands
None
Opcode
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1
0
1
0
0
0
0
0
0
1
1
1
1
1
0
1
Execution
Increment PC, then ...
(ACC) – shifted (PREG)
→
ACC
Status Bits
Affected by
Affects
PM and OVM
C and OV
This instruction is not affected by SXM.
Description
The content of PREG, shifted as defined by the PM status bits, is subtracted
from the content of the accumulator. The result is stored in the accumulator.
SPAC is not affected by SXM, and the PREG value is always sign extended.
The function of the SPAC instruction is a subtask of the LTS, MPYS, and SQRS
instructions.
Words
1
Cycles for a Single SPAC Instruction
ROM
DARAM
SARAM
External
1
1
1
1+p
Cycles for a Repeat (RPT) Execution of an SPAC Instruction
ROM
DARAM
SARAM
External
n
n
n
n+p
Example
SPAC
;(PM = 0)
Before Instruction
After Instruction
PREG
10000000h
PREG
10000000h
ACC
X
70000000h
ACC
1
60000000h
C
C
Cycles