Using Bits From a Variable

[KevKelley]

I was looking at possibly freeing up variables if necessary and was curious if you could use part of a variable for a counter and the rest for bit operations?

 

So based of my understanding, say I have a counter and it only ever used up to 4 bits (%00000000 - %00001010).

 

Can I use the 4 bits that are never used or when a variable is used does it check all of the bits?

 

So if I were to check for x{7} while having the counter at 10 (%10001010), would it read both or by turning on x{7} would it be read as 138?

[Lillapojkenpåön]

There's only one bit 7, but the counter would be 138, you can turn the first half into a four bit variable aka nibble, it can only count to 15.

 

 

   macro _Set_Lo_Nibble

   {1}=(({2}^{1})&$0F)^{1}

end

 

   def PEEK_Counter = x&$0F

   def POKE_Counter = callmacro _Set_Lo_Nibble x

 

 

To set it to 0

POKE_Counter 0 ;notice no equal sign

 

To check if it's 15

if PEEK_Counter = 15 then...

 

To add 1

temp5 = (PEEK_Counter) + 1 

POKE_Counter  temp5

 

Then you can use bits 4-7 for other things, it won't affect peeking at the counter since it only checks the first four bits

 

 

[KevKelley]

Ah. Okay. Thanks! I remember reading about nybble variables early on but never knew what for but now it makes sense. I will definitely play around with this. 

 

So then if I have it count up and need to change back to 0 then I would do:

 

If PEEK_Counter = 15 then POKE_Counter 0

 

And then add to it using a temp variable.

 

I'm sure I'll get the hang of this. Thanks very much!