At 03:08 PM 3/14/01 -0800, you wrote:
>Given the following code snippets, would someone be nice enough to explain
>why method-1 gets a fixup overflow error, but method-2 does not. I
>understand why method-1 generates an error, but do not understand how
>method-2 fixes it when both "movwf  (_dlyctr ^0x80)" and "movwf  _dlyctr"
>compile to 00B4. (Setting bank select bits in the STATUS register to bank-1
>or not makes no difference)
>
>bank1 unsigned char dlyctr;  (compiler places "dlyctr" at 0xB4)
>
>method-1
>#asm
>        movlw       0x03
>        movwf       _dlyctr
>        decfsz      _dlyctr,f
>#endasm
>
>method-2
>#asm
>        movlw       0x03
>        movwf       (_dlyctr ^0x80)
>        decfsz      (_dlyctr^0x80),f
>#endasm
>
>
>Sam....

Assuming you understand that (_dlyctr^0x80) should evaluate to 0x34,
then you probably looked at the compiled code and saw 0xB4, but
didn't realize that it's the movwf opcode that provided the "extra"
bit.  It's just a lookalike.

  movwf = 00 0000 1xxx xxxx
  0x34  =          011 1000
               ----------------
 "0xB4" = 00 0000 1011 1000

Barry

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