Getting multiple bits from variable by alias.

CuriousOne

The topic title is a bit strange, but I have no words to describe otherwise what I need.

Quote from help:

rhino   [COLOR=#000000][B]VAR[/B][/COLOR]     Word                    ' A 16-bit variable
eye     [COLOR=#000000][B]VAR[/B][/COLOR]     rhino.BIT9              ' A bit

But what if I want eye variable to be a byte, which bits start from BIT2 to BIT9 of variable rhino ?

How should I ?

Hal Albach

rhino     VAR     WORD
rhino  =  rhino    >> 2
eye      VAR     rhino.LOWBYTE

If the WORD rhino has to be preserved then copy it to another WORD variable and shift that one

rhino     VAR     WORD
.
.
.
TempRhino    =   rhino
TempRhino  =  TempRhino    >> 2
eye      VAR    TempRhino.LOWBYTE

Mike Green

Hal Albach has most of it. To extract the 8 bits from bits 2..9 of a word, you'd write

eye = (rhino >> 2) & $FF

To store into a section of a word, you have to preserve the rest of the word like this

rhino = (rhino & $FC03) | (eye << 2)

In these cases, "eye" is a temporary byte variable. There is no way to declare a name for a portion of another variable except for nibbles and bytes.

Chris Savage

CuriousOne wrote: »

But what if I want eye variable to be a byte, which bits start from BIT2 to BIT9 of variable rhino ?How should I ?

If you align the bits you want to be from 0 to 7 you could use:

rhino   [COLOR=#000000][B]VAR[/B][/COLOR]     Word                    ' A 16-bit variable
eye     [COLOR=#000000][B]VAR[/B][/COLOR]     rhino.lowbyte       ' Lower Byte

Likewise you could use a nibble if needed for 4-bits at a time. If you really need them offset like you mentioned then you would have to do it the way Hal and Mike described.