Measure internal cycles needed for an operation

[Yinon]

Hello !

I have to measure the No. of cycles needed for loop like:


movlw 0x20,N
DELAY: decfsz 0x20
goto DELAY

( or more complicated loops )
is it equals to: 1+(N-1)+2 + (N-1) ?
___________________________
This message was ported from CCS's old forum
Original Post ID: 144515251

[R.J.Hamlett]

:=Hello !
:=
:=I have to measure the No. of cycles needed for loop like:
:=
:=
:= movlw 0x20,N
:=DELAY: decfsz 0x20
:= goto DELAY
:=
:=( or more complicated loops )
:=is it equals to: 1+(N-1)+2 + (N-1) ?
Simplest way. Load the hex file into the MPLAB simulator, add a breakpoint in front of the code, and immediately after the code, open the stopwatch window, and run it.
You can do it 'by hand', by using the chips data sheet, by looking at the cycles needed for each operation. In the case given:
movlw 0x20,N
//One cycle - four clocks
DELAY: decfsz 0x20
//One cycle, when no skip. Three cycles for the 'skip', when
//the next instruction is a two cycle instruction (GOTO).
goto DELAY
//Two cycles.
Starting with twenty, the test will be '19' on the first pass,
and will execute 19 times as a loop, and then once as the skip past. So the code will take:
1+((1+2)*19)+3 cycles = 61 cycles

Best Wishes
___________________________
This message was ported from CCS's old forum
Original Post ID: 144515254