Chapter 16
Appendix
XVI - 74 Extension Instruction Specification
4) Precautions for describing byte data multiply and accumulate instruction and multiply and accumulate
instruction
When a byte data multiply and accumulate instruction and multiply and accumulate instruction are
executed continuously, the result of the byte data multiply and accumulate instruction is used to execute
the multiply and accumulate instruction. For this reason, the next multiply and accumulate instruction
must be activated after the result of the byte data multiply and accumulate instruction, that is required for
the multiply and accumulate instruction, has been output. Therefore, it is necessary to provide 1 cycle
between the preceding byte data multiply and accumulate instruction and the succeeding multiply and
accumulate instruction.
Figure:16.4.6 Drawing of Pipelining for Precaution (4)
This precaution is applicable to the following instructions:
<Byte data multiply and accumulate instructions>
MACB, MACIB, MACBU and MACIBU instructions
<Multiply and accumulate instructions>
MAC, MACI, MACH, MACIH, MACU, MACIU, MACHU, MACIHU, MACB, MACIB,
MACBU and MACIBU instructions
DEC
Byte data multiply and
accumulate instruction (1)
Insert 1 cycle
Multiply and accumulate
instruction (2)
Instruction
decoding
Instruction
decoding
Operation
Operation
Multiply and accumulate
instruction (1) outputs
the result required for
multiply and accumulate
instruction (2)
EX
MEM
WB
Result available
for reference
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