Texas Instruments TMS320C28x Reference Manual page 305

MAC P ,loc16,*XAR7/++
Flags and
Z
Modes Modes
N
C
V
OVC
OVM
PM
Repeat
Example
; Calculate sum of product using 16-bit multiply:
; int16 X[N]
; int16 C[N]
; sum = 0;
; for(i=0; i < N; i++)
; sum = sum + (X[i] * C[i]) >> 5;
MOVL
MOVL
SPM
ZAPA
RPT
||MAC
ADDL
MOVL
6-148
After the addition, the Z flag is set if the ACC value is zero, else Z is cleared.
After the addition, the N flag is set if bit 31 of the ACC is 1, else N is cleared.
If the addition generates a carry, C is set; otherwise C is cleared.
If an overflow occurs, V is set; otherwise V is not affected.
If overflow mode is disabled; and if the operation generates a positive
overflow, then the counter is incremented. If overflow mode is disabled; and if
the operation generates a negative overflow, then the counter is
decremented.
If overflow mode bit is set; then the ACC value will saturate maximum
positive (0x7FFFFFFF) or maximum negative (0x80000000) if the operation
overflowed.
The value in the PM bits sets the shift mode for the output operation from the
product register. If the product shift value is positive (logical left shift
operation), then the low bits are zero filled. If the product shift value is
negative (arithmetic right shift operation), the upper bits are sign extended.
This instruction is repeatable. If the operation follows a RPT instruction, then
it will be executed N+1 times. The state of the Z, N, C and OVC flags will
reflect the final result. The V flag will be set if an intermediate overflow
occurs.
; Data information
; Coefficient information (located in low 4M)
XAR2,#X
XAR7,#C
−5
#N−1
P,*XAR2++,*XAR7++
ACC,P << PM
@sum,ACC
; XAR2 = pointer to X
; XAR7 = pointer to C
; Set product shift to ">> 5"
; Zero ACC, P, OVC
; Repeat next instruction N times
; ACC = ACC + P >> 5,
; P = *XAR2++ * *XAR7++
; Perform final accumulate
; Store final result into sum