Renesas M32R-FPU, Software Manual

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APPENDICES
APPENDICES-12
M32R-FPU Software Manual (Rev.1.01)
(2) Pipeline Flow with Stalls
A pipeline stage may stall due to execution of a process or branch instruction.
The following diagrams show typical stall cases.
<Case 1> An instruction which requires several cycles is executed in E
IF D E WB DIV R1,R2 E E
IF D stall WB
ADD R3,R4
E stall
IF D WB E stall stall
IF D stall WB E stall
ADD R5,R6
ADD R7,R8
<Case 2> An instruction which requires more than 1 cycle for its operand access is executed
IF D E WB
LD R1,@R2
MEM1
IF D WB E stall
IF D stall WB E
IF D WB E stall
ADD R5,R6
ADD R7,R8
MEM1
MEM2 MEM1
LD R3,@R4
MEM2 MEM1
••••
stall
••••
stall
••••
stall
••••
Other than no-wait
memory access
••••
••••
••••
••••
stall: a pipeline stall
Appendix Figure 3.2.3 Pipeline Flow with Stalls (1)
APPENDIX 3
Appendix 3 Pipeline Processing