Lookup tables in VAR blocks?

Jack Buffington

I tacked this onto a previous topic but that topic was a little old and didn't get any replies...


Does anyone know how to initialize an array in a VAR block with pre-defined values. I need to pass the address of the lookup table to an assembly program. The lookup table will be followed by other variables that the assembly will need to reference. I can create a lookup table in a DAT block and then reference it from SPIN like this but that won't work for me directly.

DAT

lookupTable long        1,2,3,4,5,6,7,8,9,10

PUB start

  dira := $FFFFFFFF
  repeat
     outa := lookupTable

I could do something like this but it sucks up another chunk of HUB RAM the same size as the lookup table. I'm tight on HUB RAM so I would prefer to not do that.

DAT
lookupTable long        1,2,3,4,5,6,7,8,9,10

VAR
long    theTable[noparse][[/noparse]10]
long    count
  
PUB start

  repeat count from 0 to 9
    theTable[noparse][[/noparse]count] := lookupTable[noparse][[/noparse]count]

  cognew(@PmyAssemblyStart,@theTable[noparse][[/noparse]0])   

Is there some way to just initialize an array from within the VAR block. I'm not seeing anything in the propeller manual.

Phil Pilgrim (PhiPi)

You can pass the hub address of a DAT block to an assembly cog the same as you do a VAR array. For your "other variables" that you need to pass, just tack them onto the end of the DAT block, initialized to zeroes, instead of declaring them as VARs.

-Phil

Dave Hein

If you are providing a list of variables to the the assembly routine you can just add the address of the DAT table to the variable list.· Something like this:

DAT
lookupTable long        1,2,3,4,5,6,7,8,9,10 
 
VAR
long    varlist[noparse][[/noparse]3]
  
PUB start(arg1, arg2) 
  varlist[noparse][[/noparse]0] := arg1
  varlist[noparse][[/noparse]1] := arg2
  varlist[noparse][[/noparse]2] := @lookupTable
  cognew(@PmyAssemblyStart,@varlist)   
 

mpark

Your other post did get replies. Did you even look?

Jack Buffington

Got it! Thanks!

One gotcha that I found was that the compiler seems to join multiple DAT sections into one address space so if I declare my variables in one file, I have to put my program in another file, which is what I normally do but for the sake of testing things out, I didn't.

For those of you searching for this same thing, here is the code that I wrote and tested:

In one file:

OBJ
        DISPLAY : "lookup02.spin"  
DAT
temp3         long      0                       ' this is here to keep things long aligned
lookupTable   long      1,2,3,4,5,6,7,8,9,10
otherVariable long      0
anotherTable  long      $FF[noparse][[/noparse]600]                ' create a table 

PUB start

  
  otherVariable := 37
  anotherTable[noparse][[/noparse]99] := 16
  anotherTable[noparse][[/noparse]100] := 17
  anotherTable[noparse][[/noparse]101] := 18
  DISPLAY.Start(@lookupTable[noparse][[/noparse]0]) 

In the other file:

PUB Start  (address)
  cognew(@startDisplay,address)

DAT

startDisplay  mov       dira,#255
              mov       temp,par
              add       temp,#40                ' skip over the 10 lookupTable variables
              add       temp,#4                 ' skip over otherVariable
              add       temp,#400               ' skip over 100 variables in anotherTable
              rdbyte    temp2,temp
              mov       outa,temp2            ' output shows 17

AA            jmp       #AA
temp    long  0
temp2   long  0

Post Edited (Jack Buffington) : 4/2/2010 9:36:37 PM GMT

Jack Buffington

mpark,

I didn't see any e-mail notice from the forum so I posted again. In looking back now, I see that it was there after all. Sorry for the repost and thanks for your reply on the other thread.

Phil Pilgrim (PhiPi)

You can reset the cog address pointer using the ORG statement. That way each distinct block of assembly code in a DAT section has its own start address, viz:

DAT
[s]temp3         long      0                       ' this is here to keep things long aligned[/s] NOT NECESSARY
lookupTable   long      1,2,3,4,5,6,7,8,9,10
otherVariable long      0
anotherTable  long      $FF[noparse][[/noparse]600]                ' create a table 

PUB start  
  otherVariable := 37
  anotherTable[noparse][[/noparse]99] := 16
  anotherTable[noparse][[/noparse]100] := 17
  anotherTable[noparse][[/noparse]101] := 18
  cognew(@startDisplay,@lookupTable)

DAT
              [b]org       0[/b]

startDisplay  mov       dira,#255
              mov       temp,par
              add       temp,#40                ' skip over the 10 lookupTable variables
              add       temp,#4                 ' skip over otherVariable
              add       temp,#400               ' skip over 100 variables in anotherTable
              rdbyte    temp2,temp
              mov       outa,temp2            ' output shows 17

AA            jmp       #AA
temp    long  0
temp2   long  0

-Phil