MAC P,loc16,0:pma
6-145
MAC P,loc16,0:pma Multiply and Accumulate
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
MAC P,loc16,0:pma 0001 0100 LLLL LLLL
CCCC CCCC CCCC CCCC
X − n+2
Operands P Product register
loc16 Addressing mode (see Chapter 5)
0:pma Immediate program memory address, access low 64K range of program
space only (0x000000 to 0x00FFFF)
Description 1) Add the previous product (stored in the P register), shifted as specified
by the product shift mode (PM), to the ACC register.
2) Load the T register with the content of the location pointed to by the
“loc16” addressing mode.
3) Multiply the signed 16-bit content of the T register by the signed 16-bit
content of the addressed program memory location and store the 32-bit
result in the P register:
ACC = ACC + P << PM;
T = [loc16];
P = signed T * signed Prog[0x00:pma];
The C28x forces the upper 6 bits of the program memory address, specified
by the “0:pma” addressing mode, to 0x00 when using this form of the MAC
instruction. This limits the program memory address to the low 64K of
program address space (0x000000 to 0x00FFFF). On the C28x devices,
memory blocks are mapped to both program and data space (unified
memory), hence the “0:pma” addressing mode can be used to access data
space variables that fall within its address range.
Flags and
Z After the addition, the Z flag is set if the ACC value is zero, else Z is cleared.
Modes
N After the addition, the N flag is set if bit 31 of the ACC is 1, else N is cleared.
C If the addition generates a carry, C is set; otherwise C is cleared.
V If an overflow occurs, V is set; otherwise V is not affected.
OVC 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.
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