Vasile Surducan wrote:
> Ok, I hate C ! Maybe you help me and translate this "ugly code":

Why do you hate C ? What did it do to you ?

//read byte from SPI (mode 3) as a master
;BYTE rdSPI(void)
;{
SrsSPI:
;  register BYTE BitCnt = 8;   counter 8 bit
        movlw   8
        movwf   BitCnt
;  register BYTE Shift;        auxiliary register
        ;; somewhere a register Shift is declared (cblock etc)
;   do                          begin ?
rsSPI_L0:
;   {
;      SPI_SCK_LO();            spi_sclk_lo = low ?
        bcf     Fspi,Bspiclk    ;; just guessing (plp)
;     Shift <<= 1;             asm rlf shift ?
        rlf     Shift,f
;      if(IS_SPI_SDI_LO())
        movlw   IS_SPI_SDI_LO_MASK      ;; one bit set to select
        andwf   Fspi,w                  ;; Z if LO
        btfss   STATUS,Z
        goto    rsSPI_L1
;         Shift &= ~1;         this one is the hell thing !!!
        movlw   1               ;; deliberately not optimized so you can
        xorlw   0xFF            ;; see it (plp)
        andwf   Shift,f
        goto    rsSPI_L2
;      else
rsSPI_L1:
;         Shift |= 1;          same this one !
        movlw   1               ;; hehe
        iorwf   Shift,f
rsSPI_L2:
;      SPI_SCK_HI();
        bsf     Fspi,Bspiclk    ;; just guessing (plp)
;   } while (--BitCnt);        ok here repeat 8 times
        decfsz  BitCnt,f
        goto    rsSPI_L0
;}
        return  0

There are other more efficient ways to write the assembly. The compiler
would probably outdo me easily ;-). If you are confused by a compound
expression rewrite it as several simpler expressions like:

  Shift &= ~1;

  tmp = ~1;
  tmp1 = Shift & tmp;
  Shift = tmp;

~1 is the 1's complement of 1 on the domain Shift it defined on (i.e. a
Byte), thus ~1 is 0xFF-1 = 0xFE. When you see something like <operator>=
in C it simply means:

  <variable> <operator>= <expression>;

  <variable> = <variable> <operator> <expression>;

Peter

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