ASM cycles in PICBASIC

[Bruce]

Here's one version using a modified PBP library routine & macro;

Result VAR BYTE BANK0 SYSTEM
I      VAR BYTE BANK0 SYSTEM
Temp   VAR BYTE BANK0 SYSTEM
X      VAR BYTE

    TRISB.4 = 1
    Result = 0
    
Main:
    for I = 0 to 7       ' loop x 8
      X = 0
      while X < 10       ' Test pin x 10
        if PORTB.4 = 1 then
         call BitSet     ; Result.0[I] = 1
        else            
         call BitClear   ; Result.0[I] = 0
        endif
        X = X + 1 
      wend
    next I

Done:
    goto   Done
	
BitClear:
ASM
    call   ConvertBit  ; Bitmask -> W
    movwf  Temp        ; W -> Temp
    comf   Temp,F      ; Invert Temp
    movf   Temp,W      ; Temp -> W
    andwf  Result,F    ; AND W with Result
    return
ENDASM

BitSet:
ASM
    call   ConvertBit  ; Bitmask -> W
    iorwf  Result,F    ; OR W with Result
    return
    
;******************************************************
;* Input      : I = bit (0 - 7)                       *
;* Output     : W = bit mask                          *
;* Notes      : Modified example from PBP library     *
;******************************************************
ConvertBit              ; See pbppic14.lib CONVBIT & TABLE?C macro
    movlw   btable >> 8 ; Get high address of jump table
    movwf   PCLATH      ; Set program counter latch high
    movf    I,W         ; Get bit number from I into W reg
    andlw   07h         ; Isolate lower 3 bits (only works with 0-7)
    TABLE?C 08h         ; PBP library macro for table alignment
btable                  ; Returns from table with bit mask in W reg
    retlw   01h         ; %00000001
    retlw   02h         ; %00000010
    retlw   04h         ; %00000100
    retlw   08h         ; %00001000
    retlw   10h         ; %00010000
    retlw   20h         ; %00100000
    retlw   40h         ; %01000000
    retlw   80h         ; %10000000
ENDASM

    END

You can learn a good deal about assembly language by reading through the
PBP library.

[Darrel Taylor]

breeno,

In the original example (basic version), the while loops 10 times, reading the pin and overwriting the same bit in the CODE variable. It's no different than just reading it once (other than time used).

So, with that in mind, here's another possibility...

ASM
   MOVE?CB  8, _i
IN_Loop
   MOVE?TT  _in, STATUS, C
   CHK?RP   _CODE
   rrf      _CODE, F
   CHK?RP   _i
   decfsz   _i, F
   goto     IN_Loop
ENDASM

It just reads the pin, put's the value in the Carry flag, then rotates it into the CODE variable (8 times).