Move seperate bytes into a word

[Ioannis]

Something like this?

z=a+b<<4+c<<8+d<<12

Ioannis

[tazntex]

Thank you very much, never thought of that. I will try it out.

[mister_e]

"Z" holds
A= 0-3,
B= 4-7,
C=8-11,and
D=12-15.

First thing is to isolate each 4LSB of each variable. Easy way, using boolean AND (&)

A = A & $0F
B = B & $0F
C = C & $0F
D = D & $0F

Now, you need to shift some bits of your Bytes variables. This is done using left shift (<<). Check your manual about that. Knowing that, we could modify the above like

A = A & $0F
B = B << 4  
C = C & $0F
D = D << 4

Now you need to combine A & B, and C & D, then the whole thing together. Boolean OR do the trick

A = (A & $0F) | (B <<4)  ' a hold A & B
C = (C & $0F) | (D <<4)  ' C hold C & D

Then you need to send A and C where they're suppose to go in Z

Z.LowByte = A
Z.HighByte = C

A is now LSB of Z(0-7), C is now MSB of Z(8-15).

This could be shorten like

Z.LowByte = (A & $0F) | (B <<4)  
Z.HighByte = (C & $0F) | (D <<4)

If you're REALLY SURE you NEVER EVER mess with bits <7:4> of your variables, then yes, this could reduce to

Z.HighByte = (D<<4) | C
Z.LowByte = (B<<4) | A

OR

Z = (D<<12) | (C<<8) | (B<<4) | A

I see other ways, but this should be more than enough to start

[mister_e]

One step further..

Z VAR WORD
A VAR Z.LOWBYTE
B VAR BYTE
C VAR Z.HIGHBYTE
D VAR BYTE

'
'    Some other code where you set A, B, C & D BYTE variables
'

Z.HIGHBYTE = Z.HIGHBYTE | (D<<4)
Z.LOWBYTE = Z.LOWBYTE | (B<<4)
' Now you have everything in Z... easy huh?

or.. yet another

Z = Z | (B<<4) | (D<<12)

Enjoy

[tazntex]

I've tried Ioannis suggestion and it seems to work fine, I'll will try the others to. I do not plan to ever use bits 7-4 so I will give these a try. I am just playing around trying to see what does and does not work. I learned something new and appreciate all the help.

Again, Many Thanks

[Ioannis]

Steve's solutions cover the case that high nibble could hold some bits at 1 and masks to zero. Mine is based on the assumption that high nibbles will always be 0.

It would also be interesting to know which way is less memory hungry.

Ioannis

[mister_e]

this one

Z VAR WORD
A VAR Z.LOWBYTE
B VAR BYTE
C VAR Z.HIGHBYTE
D VAR BYTE

'
'    Some other code where you set A, B, C & D BYTE variables
'

Z.HIGHBYTE = Z.HIGHBYTE | (D<<4)
Z.LOWBYTE = Z.LOWBYTE | (B<<4)

ought to be the the less memory hungry.

while changing the last two line by

Z = Z | (B<<4) | (D<<12)

should use more code space.

In the above A & C are Aliases, so shouldn't need any extra RAM.

this

z=a+b<<4+c<<8+d<<12

ought to use load of RAM and time to execute... BUT this said, I'm rusty and my memory/capacity fade since few months...

[Darrel Taylor]

Here's one that won't get used.
But since the questions of how big and how fast came up, you won't find anything smaller or faster. (unless Bruce shows up)

GroupVars  VAR BYTE[6]
  A    VAR GroupVars(0)
  B    VAR GroupVars(1)
  C    VAR GroupVars(2)
  D    VAR GroupVars(3)
  ZW   VAR WORD EXT : @ZW = _GroupVars + 4

ASM
    CHK?RP _GroupVars
    swapf  _D, W     ; swap nibbles in D
    iorwf  _C, W     ; or with C
    movwf  ZW + 1    ; move to Highbyte of word
    swapf  _B, W     ; swap nibbles in B
    iorwf  _A, W     ; or with A
    movwf  ZW        ; move to LowByte of word
ENDASM