How to address bits in a Byte

bsnut

Is it possible to address bits in a byte or longs in Spin?

I know how to do it with Basic Stamps and also understand may have to use the binary numbers to do what I want in Spin. Is this what, I have to do?

lanternfish

You can use the bitwise operators similarly to Stamp BASIC. Check the posts listed below in the Similar Threads box

bill190

You can pick out a specific bit or bits with the help of left shift, right shift, AND, and the use of a "mask".

(Using short numbers for demonstration...)
0010 left shift would be 0100
0010 right shift would be 0001

Then you can pick out specific bits using AND with a "mask"...

1011 AND with mask 0001 would be 0001
1010 AND with mask 0001 would be 0000

1011 AND with mask 0010 would be 0010
1001 AND with mask 0010 would be 0000

1011 AND with mask 1111 would be 1011

The "mask" is whatever you want to make it. The 1's in the mask being the bits you want to pick out.

JonnyMac

I have these methods built into my standard programming template.

pub getbit(target, pos)

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

  return (target >> pos) & 1


pub putbit(target, pos, value)

'' writes value.0 to target.pos

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


pub togglebit(target, pos)

'' toggles target.pos

  return target ^ (1 << pos)

Note that when porting BASIC Stamp code to the Propeller you won't always want to use these methods, you may end up with inline code as it's more efficient (e.g., duplicating SHIFTIN or SHIFTOUT).

bsnut

Thanks Jon I can see how different it is with the Propeller.

Is there way I can get copy of the templale you use

JonnyMac

Is there way I can get copy of the template you use

It's attached. I prefix it with underscores to force it to the top of the files pane in the Propeller Tool -- makes it easy to find.