Setting a single bit in Spin

Rumple

I can't believe I've never tried to do this before. What's the best way to set and reset a single bit of a long in Spin? I've always assumed it was "someregister[0]~~ ",since "outa[0]~~" works, but apparently that's not it.

Something with "|<" in it maybe?

Duane Degn

This will set a single bit:

singleBitMask := |< pinNumber

To "or" one mask to another (oring enableMask on to activeMask)

activeMask |= enableMask

To turn off these same bits (same function as "andn" in PASM):

activeMask &= !enableMask  

Thanks to my fellow forum members for this useful stuff.

David Carrier

To set a bit use this:

variable |= |< bit

It will decode the bit, which creates a value with only that bit high, then OR the result into the variable.

To clear a bit use this:

variable &= ! |< bit

It will decode the bit, which creates a value with only that bit high, invert it, which makes all bits high except the one you are clearing, then AND the result into the variable, effectively clearing that bit within the variable.

— David Carrier
Parallax Inc.

Rayman

I like to use the unused INB, OUTB and DIRB registers for this...

Just copy the long you want to work with to DIRB and then Spin will let you do dirb[SomeBit]:=1 and things like that...

Rumple

Nailed it. Thanks for your help guys.

Also, that's brilliant, Rayman.

Harprit

How about reading one bit,or a range with compact code
H

JonnyMac

How about reading one bit,or a range with compact code

bitval := (testval >> bitpos) & %1

If you want to read a group, set bitpos to the LSB value and change the & %1 to something that fits your group; for a nibble it would be & %1111.

Rayman

reading a range is really easy using, e.g., INB too...
For example, you can set bits 4 through 9 to a value like this: INB[4..9]:=value
You can even set them backwards like this: INB[9..4]:=value

Harprit

Thanks guys
I am just finishing up the beginners book and I can add this great stuff to it.
Just in time.
H