PBP command execution time

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  1. - 16th December 2014, 03:25 #1
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    Default PBP command execution time

    Main logic snippet:
    Code:
    ...
mainloop:
    TRISA = %11111100
    PORTA = %00000001

    PORTA = %00000010
    goto mainloop
End
    ASM listing:
    Code:
    ...
	LABEL?L	_mainloop	
	MOVE?CB	0FCh, TRISA
	MOVE?CB	001h, PORTA
	MOVE?CB	002h, PORTA
	GOTO?L	_mainloop
	END?	

	END
    Saleae sampling:
    Name: Saleae Charlie-plex 2 pins.PNG Views: 736 Size: 43.0 KB

    1 uSec per instruction at 8MHz on a 18F44K22.

    Is it that simple? Or is there more going on and I'm not getting it?

    (1978-1984 is so far away. Yeah, I didn't have sec 5 math so I had to take it before starting 3-yr data processing program. Of course I dropped out sec 5 math on first try; culture shock coming from high school where teachers kicked me in the butt to get things done and had to come back the next September to get it done.)

    Robert
  2. - 16th December 2014, 03:44 #2
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    Default Re: PBP command execution time

    @8mhz each instruction takes 0.5uS what you are looking at there are macro's you need the asm to see the actual code


    it wood go something like

    mainloop:
    movf 0fh,w
    movwf trisa
    movf 1,w
    movwf porta
    movf 0,w
    movwf porta
    goto mainloop

    ps pbp probably sticks a clrwdt in there somewhere too
    Last edited by richard; - 16th December 2014 at 03:47. Reason: ps
  3. - 16th December 2014, 03:56 #3
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    Default Re: PBP command execution time

    I found this by looking for mainloop in the LST file:

    Code:
    ...
                      00086         LABEL?L _mainloop       
                          M         RST?RP
                          M     if (PREV_ALT != 0)
                          M         bcf     WDTCON, ADSHR
                          M PREV_ALT = 0
                          M     endif
                          M     if (PREV_BANK != 0)
                          M         movlb   0
                          M PREV_BANK = 0
                          M     endif
                          M     ifdef PM_USED
                          M         LALL
                          M _mainloop
                          M         XALL
                          M     else
000074                    M _mainloop
                          M     endif
                      00087         MOVE?CB 0FCh, TRISA
                          M         CHK?RP  TRISA
                          M     if (((TRISA) & 8000h) != PREV_ALT)
                          M       if ((TRISA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (TRISA) & 8000h
                          M     endif
                          M     if ((((TRISA) & 0fffh) > BANKA_END) & (((TRISA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((TRISA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (TRISA)
                          M PREV_BANK = high (TRISA)
                          M       endif
                          M     endif
                          M     if (low (0FCh) == 0)
                          M         clrf    TRISA
                          M     else
                          M       if (low (0FCh) == 255)
                          M         setf    TRISA
                          M       else
000074 0EFC               M         movlw   low (0FCh)
000076 6E92               M         movwf   TRISA
                          M       endif
                          M     endif
MPASM  5.49                      BLINK1~1.ASM   12-15-2014  22:49:14         PAGE 15


LOC  OBJECT CODE     LINE SOURCE TEXT
  VALUE

                      00088         MOVE?CB 001h, PORTA
                          M         CHK?RP  PORTA
                          M     if (((PORTA) & 8000h) != PREV_ALT)
                          M       if ((PORTA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (PORTA) & 8000h
                          M     endif
                          M     if ((((PORTA) & 0fffh) > BANKA_END) & (((PORTA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((PORTA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (PORTA)
                          M PREV_BANK = high (PORTA)
                          M       endif
                          M     endif
                          M     if (low (001h) == 0)
                          M         clrf    PORTA
                          M     else
                          M       if (low (001h) == 255)
                          M         setf    PORTA
                          M       else
000078 0E01               M         movlw   low (001h)
00007A 6E80               M         movwf   PORTA
                          M       endif
                          M     endif
                      00089         MOVE?CB 002h, PORTA
                          M         CHK?RP  PORTA
                          M     if (((PORTA) & 8000h) != PREV_ALT)
                          M       if ((PORTA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (PORTA) & 8000h
                          M     endif
                          M     if ((((PORTA) & 0fffh) > BANKA_END) & (((PORTA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((PORTA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (PORTA)
                          M PREV_BANK = high (PORTA)
                          M       endif
                          M     endif
                          M     if (low (002h) == 0)
                          M         clrf    PORTA
                          M     else
                          M       if (low (002h) == 255)
                          M         setf    PORTA
                          M       else
00007C 0E02               M         movlw   low (002h)
00007E 6E80               M         movwf   PORTA
                          M       endif
                          M     endif
                      00090         MOVE?CB 0F3h, TRISA
MPASM  5.49                      BLINK1~1.ASM   12-15-2014  22:49:14         PAGE 16


LOC  OBJECT CODE     LINE SOURCE TEXT
  VALUE

                          M         CHK?RP  TRISA
                          M     if (((TRISA) & 8000h) != PREV_ALT)
                          M       if ((TRISA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (TRISA) & 8000h
                          M     endif
                          M     if ((((TRISA) & 0fffh) > BANKA_END) & (((TRISA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((TRISA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (TRISA)
                          M PREV_BANK = high (TRISA)
                          M       endif
                          M     endif
                          M     if (low (0F3h) == 0)
                          M         clrf    TRISA
                          M     else
                          M       if (low (0F3h) == 255)
                          M         setf    TRISA
                          M       else
000080 0EF3               M         movlw   low (0F3h)
000082 6E92               M         movwf   TRISA
                          M       endif
                          M     endif
                      00091         MOVE?CB 004h, PORTA
                          M         CHK?RP  PORTA
                          M     if (((PORTA) & 8000h) != PREV_ALT)
                          M       if ((PORTA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (PORTA) & 8000h
                          M     endif
                          M     if ((((PORTA) & 0fffh) > BANKA_END) & (((PORTA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((PORTA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (PORTA)
                          M PREV_BANK = high (PORTA)
                          M       endif
                          M     endif
                          M     if (low (004h) == 0)
                          M         clrf    PORTA
                          M     else
                          M       if (low (004h) == 255)
                          M         setf    PORTA
                          M       else
000084 0E04               M         movlw   low (004h)
000086 6E80               M         movwf   PORTA
                          M       endif
                          M     endif
                      00092         MOVE?CB 008h, PORTA
                          M         CHK?RP  PORTA
MPASM  5.49                      BLINK1~1.ASM   12-15-2014  22:49:14         PAGE 17


LOC  OBJECT CODE     LINE SOURCE TEXT
  VALUE

                          M     if (((PORTA) & 8000h) != PREV_ALT)
                          M       if ((PORTA) & 8000h)
                          M         bsf     WDTCON, ADSHR
                          M       else
                          M         bcf     WDTCON, ADSHR
                          M       endif
                          M PREV_ALT = (PORTA) & 8000h
                          M     endif
                          M     if ((((PORTA) & 0fffh) > BANKA_END) & (((PORTA) & 0fffh) < (0f01h + BANKA_END)))
                          M       if (((PORTA) & 0f00h) != (PREV_BANK << 8))
                          M         movlb   high (PORTA)
                          M PREV_BANK = high (PORTA)
                          M       endif
                          M     endif
                          M     if (low (008h) == 0)
                          M         clrf    PORTA
                          M     else
                          M       if (low (008h) == 255)
                          M         setf    PORTA
                          M       else
000088 0E08               M         movlw   low (008h)
00008A 6E80               M         movwf   PORTA
                          M       endif
                          M     endif
                      00093         GOTO?L  _mainloop
                          M         L?GOTO  _mainloop
...
    A lot more going on before and after that snippet.

    Robert
  4. - 16th December 2014, 04:07 #4
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    Default Re: PBP command execution time

    that why your own asm routines are often used , if you know every thing is in the same mem bank then ALL that bank ckecking (chk:rp) can be eliminated ,but what you have there is a lst file I would expect any decent compiler to optimise most if not all that unnecessary code out , the assembled file should look cleaner than that, but need to disassemble the hex file to see it
    Last edited by richard; - 16th December 2014 at 04:10.
  5. - 16th December 2014, 04:13 #5
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    Default Re: PBP command execution time

    When I look in the folder where I compile, I see that ASM file I copied above, plus BAS, HEX, LST, MAC and O files.

    I don't see a "trimmed" assembler file.

    Robert
  6. - 16th December 2014, 04:19 #6
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    Default Re: PBP command execution time

    When I look in the folder where I compile, I see that ASM file I copied above, plus BAS, HEX, LST, MAC and O files.
    my bad
    I really meant the actual assembled code ---- you need a disassembler to see what really happened
  7. - 16th December 2014, 04:14 #7
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    Default Re: PBP command execution time

    How do we get calculate 0.5uS again? I never remember how to do that. I'm sure the datasheet comes into play.
    each instruction takes 4 clock cycles . a clock cycle is 1/8000000 = 125nS therefore 1 instruction = 4*125 nS = 0.5uS
  8. - 16th December 2014, 04:26 #8
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    Default Re: PBP command execution time

    Quote Originally Posted by richard View Post
    each instruction takes 4 clock cycles . a clock cycle is 1/8000000 = 125nS therefore 1 instruction = 4*125 nS = 0.5uS
    Unless I can't use a Saleae probe properly, each asm macro ran in 1uS (4uS for one pass). That's not bad considering the chunk of asm in there.

    Robert
  9. - 16th December 2014, 04:00 #9
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    Default Re: PBP command execution time

    Quote Originally Posted by richard View Post
    @8mhz each instruction takes 0.5uS ...
    How do we get calculate 0.5uS again? I never remember how to do that. I'm sure the datasheet comes into play.


    ...ps pbp probably sticks a clrwdt in there somewhere too
    Yup, right after the GOTO at the bottom.

    Robert
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