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2-13 M32R-FPU Software Manual (Rev.1.01)
The MSB (Most Significant Bit) of a 32-bit instruction is always "1". The MSB of a 16-bit
instruction in the high-order halfword is always "0" (instruction A in Figure 2.2.3),
however the processing of the following 16-bit instruction depends on the MSB of the
instruction.
In Figure 2.2.3, if the MSB of the instruction B is "0", instructions A and B are executed
sequentially; B is executed after A. If the MSB of the instruction B is "1", instructions A
and B are executed in parallel.
The current implementation allows only the NOP instruction as instruction B for parallel
execution. The MSB of the NOP instruction used for word arraignment adjustment is
changed to "1" automatically by a standard Mitsubishi assembler, then the M32R-FPU
can execute this instruction without requiring any clock cycles.
16-bit instruction A 16-bit instruction B
32-bit instruction
0
16-bit instruction A 16-bit instruction B
01
0
[instruction A] --> [instruction B] sequential
< instruction execution sequence >
MSB
1
1111 0000 0000 0000
16-bit instruction A
0
0111 0000 0000 0000
inserted by assembler
32-bit instruction
1
MSB
NOP instruction whose MSB is changed to "1"
NOP instruction
[instruction A] & [instruction B] parallel
[instruction A] & [NOP] parallel
Fig. 2.2.3 Processing of 16-bit instructions
INSTRUCTION SET
2.2 Instruction format