MAC P ,loc16,*XAR7/++
6-147
MAC P ,loc16,*XAR7/++ Multiply and Accumulate
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
MAC P, loc16, *XAR7 0101 0110 0000 0111
1100 0111 LLLL LLLL
1 Y N+2
MAC P, loc16, *XAR7++ 0101 0110 0000 0111
1000 0111 LLLL LLLL
1 Y N+2
Operands P Product register
loc16 Addressing mode (see Chapter 5)
*XAR7
/++
Indirect program-memory addressing using auxiliary register XAR7, can
access full 4M x 16 program space range (0x000000 to 0x3FFFFF)
Description Use the following steps for this instruction:
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 program memory location pointed to by the XAR7 register
and store the 32-bit result in the P register. If specified, post-increment
the XAR7 register by 1:
ACC = ACC + P << PM;
T = [loc16];
P = signed T * signed Prog[*XAR7 or *XAR7++];
On the C28x devices, memory blocks are mapped to both program and data
space (unified memory), hence the “XAR7/++” addressing mode can be
used to access data space variables that fall within the program space
address range.
With some addressing mode combinations, you can get conflicting
references. In such cases, the C28x will give the “loc16/loc32” field priority
on changes to XAR7. For example:
MAC P,*−−XAR7,*XAR7++ ; −−XAR7 given priority
MAC P,*XAR7++,*XAR7 ; *XAR7++ given priority
MAC P,*XAR7,*XAR7++ ; *XAR7++ given priority
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