How to set / reset bit in the variable? (Spin)

Alarus · 2013-05-27 02:00

How to set / reset any bit in the variable?
And how to test a bit in a variable?

Regards Alarus

kuroneko · 2013-05-27 02:19

v |=  |< bit                  ' set
  v ^=  |< bit                  ' toggle
  v &= !|< bit                  ' reset

  if v & |< bit                 ' test
    ' do something

Alarus · 2013-05-27 03:44

kuroneko wrote: »

v |=  |< bit                  ' set
  v ^=  |< bit                  ' toggle
  v &= !|< bit                  ' reset

  if v & |< bit                 ' test
    ' do something

Thank you!
I wanted to use such construction:

v |=  $00000001 <- bit                      ' set
v ^=  $00000001 <- bit                      ' toggle
v &= $FFFFFFFE <- bit                       ' reset

but your beautiful.

JonnyMac · 2013-05-27 10:43

I have these methods in my standard template:

pub rd_bit(target, pos)

'' returns bit value (0..1) of target.pos

  if ((pos => 0) and (pos =< 31))
    return (target >> pos) & 1
  else
    return 0


pub wr_bit(target, pos, value)

'' writes value.0 to target.pos

  if (value & 1)
    return target | (1 << pos)
  else
    return target & !(1 << pos)

JLocke · 2013-05-28 06:42

What's the chances of getting you to post your standard template somewhere? I try to collect the pieces as I see you post these handy routines, but it would be great to get them all in a collection.
<voice of Roger Rabbit> Pleeeease, Jonny? </Rabbit off>

JonnyMac · 2013-05-28 09:15

I'm not sure how useful this will be to you or anyone else, but you're certainly welcome to it.

Rayman · 2013-05-28 18:45

This gets asked a lot...

My personal favorite way is to use the normally unused DIRB, INB, or OUTB registers...
Just like with INA, you can test and set bits in any of these...

Alarus · 2013-05-29 07:17

Which of these methods is the fastest?

Thanks for the idea Rayman.

JonnyMac · 2013-05-29 07:40

The good news is that you can use the Propeller to determine how long a snippet of code runs. I do timing tests frequently enough that I made a template just for that purpose.

How to set / reset bit in the variable? (Spin)

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