[PicForth] Re: picforth conditionals

[Samuel Tardieu]

>>>>> "Jamie" == Jamie Lawson <jlawson at ces.uoguelph.ca> writes:

Jamie> I am just starting to use Forth and in particular picforth-0.29
Jamie> and was wondering why the following statement does not seem to
Jamie> work.

Jamie> I'm waiting for a pin (sDATA) to go low or SW_Timer0 to reach
Jamie> zero.

Jamie> \*****************************

Jamie>   1 pin-b sDATA variable SW_Timer0

Jamie>   begin sDATA bit-set? SW_Timer0 @ 0 <> and while repeat

Jamie> \***************************

You may have hit a bug.

I haven't looked at the generated code yet, but I am sure that the
following will be more efficient: (speed and code space)

: waitforcond ( -- )
  begin
    sDATA bit-clr? if exit then
    SW_Timer0 0= if exit then
  again;

This has the advantage of not requiring a boolean normalization --
status bits can be used directly, as in your example a normalization
to 0 or $FF is needed in order to perform the "and" operation.

  Sam
-- 
Samuel Tardieu -- sam at rfc1149.net -- http://www.rfc1149.net/sam