XC2200 Derivatives
System Units (Vol. 1 of 2)
Central Processing Unit (CPU)
User’s Manual
4-25
V2.1, 2008-08
CPUSV2_X, V2.2
For all the other instructions that modify this kind of CSFR, a simple stall and cancel
mechanism guarantees the correct instruction flow.
A possible explicit write-operation to this kind of CSFRs is detected on the MEMORY
stage of the pipeline. The following instructions on the ADDRESS and DECODE Stage
are stalled. If the instruction reaches the EXECUTE stage, the entire pipeline and the
Instruction FIFO of the IFU are canceled. The instruction flow is completely re-started.
Conflict_Canceling_Completely:
I
n
MOV PSW,R4
I
n+1
MOV R6,R1
I
n+2
ADD R6,R1
I
n+3
MOV R3,[R0]
I
n+4
...
Table 4-15
Pipeline Dependencies with Control CSFRs (Cancel All)
Stage
T
n+1
T
n+2
T
n+3
T
n+4
T
n+5
T
n+6
DECODE
I
n+1
= MOV
R6, R1
I
n+2
= ADD
R6, R1
I
n+2
= ADD
R6, R1
–
–
I
n+1
= MOV
R6, R1
ADDRESS
I
n
= MOV
PSW, R4
I
n+1
= MOV
R6, R1
I
n+1
= MOV
R6, R1
–
–
–
MEMORY
I
n-1
I
n
= MOV
PSW, R4
–
–
–
–
EXECUTE
I
n-2
I
n-1
I
n
= MOV
PSW, R4
–
–
–
WR.BACK
I
n-3
I
n-2
I
n-1
I
n
= MOV
PSW, R4
–
–