A lil help glueing to bytes to make a word

grasshopper

I am trying to "glue" to bytes to make a word. Here is some pseudo code.

Var
  Word Glued
  Byte X, Y

Main
  X = $20
  Y = $4B

  Glued = X << 4 
  Glued = Y

This is not working as I would expect. I wanted Glued to = $204B. Perhaps some of you seasoned programmers could guide me in the right direction.

pgbpsu

@grasshopper-

Your last assignment statement "Glued = Y" blows away what you've already assigned to Glued. I think you need to do something like this:

x:=$20
y:=$4B

Glued := X << 4              ' put X in upper byte of glued
Glued := Glued | y           ' put y in lower byte of glued

I think you could also use the long/word/byte addressing in spin to do the same thing like this:

  Glued.byte[noparse][[/noparse]0]:=y          ' set lowest 8 bits of Glued to what's in Y
  Glued.byte:=x          ' set upper 8 bits of Glued to what's in X

For some reason the one of the lines above gets munched when I post . Here's my second suggestion again but not as code:
Glued.byte[noparse][[/noparse]0]:=y
Glued.byte [noparse][[/noparse] 1 ] :=x

This is explained pretty well in the manual pg 168.

pgb

Post Edited (pgbpsu) : 11/13/2008 3:31:05 PM GMT

John Abshier

Glued := x << 4 | y works

John Abshier

T Chap

If you want to put a byte into the upper 8 bytes of a word you should bitshift left 8, not 4, then OR the lower byte.

grasshopper

Thanks got it to work.

Beau Schwabe

grasshopper,

You could save a couple of variables and code space doing something like this...

Var
  Word Glued
Main
  Glued.BYTE[noparse][[/noparse]1] := $20  'X     'HIGH BYTE  
  Glued.BYTE[noparse][[/noparse]0] := $4B  'Y     'LOW BYTE

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.