Creating large array

Rus

Hello. Need help to create 256 bites long array.
I have BS2px. I get variable size too large when I try to declare array (array_name· VAR Bit (256)). I guess I am out of RAM space.
Is there any work around? I need serially shift 256 values (0 or 1), and I do not want to create several small arrays.
·
Thank you

Mike Green

The Stamps have only 26 bytes of variable space. There is a separate RAM area called "scratchpad RAM" which is 128 bytes. The last few locations have special uses, but most of that is available using the GET / PUT statements to access it a byte or a word at a time. It's not an array, but it's almost usable that way.

Zoot

If indeed you are talking about 256 *bits*, you can emulate a pseudo bit array using 32 bytes in SPRAM (scratch pad ram):

myBitArray CON 64  ' starting SPRAM address for 32 byte array, can be anywhere pretty much

index VAR Byte ' general counter

param VAR Byte ' for passing value to subroutine(s)
temp VAR param ' work var for subroutine(s)
bitVal VAR Bit

' note that at reset/powerup, all vals should be 0, this writes 1s to each bit in the pseudo array

Main:
   FOR index = 0 TO 255 ' loop through all 256 bits
     param = index ' which bit to get/set?
     bitVal = 1        ' set bit to 1
     GOSUB PUT_BIT
   NEXT

   FOR index = 0 TO 255
     param = index
     GOSUB GET_BIT
     ' now value of BIT #index is in bitVal
    DEBUG "Bit # ", DEC3 index, " = ", BIN1 bitVal, CLREOL, CR
   NEXT

END


' some subroutines:

' set param to bit # to read (0 to 255) before calling routine
' returns bit value as 0 or 1 in bitVal
GET_BIT:
  GET param >> 3 + myBitArray, temp ' get correct byte for this BIT (every 8 bits is a byte from the "stack")
  bitVal = temp.BIT0(param & $07) ' save correct bit for this byte into bitVal and return the value
  RETURN

' set param to bit # to set before calling routine
' set bitVal to value to set before calling routine
PUT_BIT:
  GET param >> 3 + myBitArray, temp ' get correct byte for this BIT (every 8 bits is a byte from the "stack")
  temp.BIT0(param & $07) = bitVal  ' set correct bit for this byte
  PUT param >> 3 + myBitArray, temp ' save it
  RETURN
 

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
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Post Edited (Zoot) : 7/24/2008 9:33:11 PM GMT

Rus

Thanks. I still need some help. I did not see Set_Bit routin.
Also , if I need insert data to index 35-40, what is the procedure?

Thank you

Zoot

Sorry, that was a typo. Should be "PUT_BIT". I fixed it above.

said...
Also , if I need insert data to index 35-40, what is the procedure?

Just set the index value, the desired bitval and it's done.

Each byte holds 8 bits. So when the param (the index) is shifted right 3 times, that divides the index by 8, resulting in byte 0-31. Then the routine gets the byte at that location in SPRAM. Then the lowest 3 bits of the param (the index bit desired) are used to set/get the bit WITHIN that byte that corresponds to the desired index.

e.g.

param = 35  ' working with bit 35 out of 0-255 bits
bitVal = 1     ' set that bit to 1
GOSUB PUT_BIT

35 >> 3 (i.e. 35/8) = 4 --> working with byte index 4 (5th byte from bytes 0-31)
35 & $07 (i.e. 35//8) = 3 --> working with bit index 3 (4th bit of byte)

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php