Need help with CODE

O.A.A. · 2010-01-12 18:34

Can someone please tell me what is happening in the following code segment :

DAT

··· ScratchPad byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

'······················ · · 0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1

PUB Main

·· DIRA := %00001111_00000011_10100000_11111111

·· OUTA := %00000000_00000000_00000000_00000000

·· waitcnt(2_000_000 + cnt)

·· workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]21]

·· If workVariable <> 0

···· Beep

···· Beep

PRI Beep

·· repeat 2

····· !outa[noparse][[/noparse]Beeper]

····· waitcnt(5_000_000 + cnt)

For some reason "workVariable" is not zero for index values 17 and onwards.

workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]17]· ·is· ·-24573

workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]19]· ·is···· 13750

workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]21]· ·is··· · 7738

workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]23]· ·is·· -28353

workVariable := word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]25]· ·is···· 30423

·Thanks.

Post Edited (O.A.A.) : 1/12/2010 6:48:59 PM GMT

Mike Green · 2010-01-12 18:43

First of all, you've defined "ScratchPad" as a sequence of bytes, yet you're referencing them as WORDs. You probably want to use the same keyword in both cases, either BYTE or WORD. There are cases where you might want to mix sizes, but you need to know what you're doing in that case.

O.A.A. · 2010-01-12 19:04

Thank you mike.
The definition of Scratchpad is as followws:
' ScratchPad(0) : indx
' ScratchPad(1) : RAC Rudder Angle Change Index
' ScratchPad(2) : RLim Rudder Limit
' ScratchPad(3) : Gain
' ScratchPad(4) : DBnd Rudder Deadband
' ScratchPad(5) : CRud Counter Rudder
' ScratchPad(6) : SHF Standing Helm Factor
' ScratchPad(7) : SpdF Speed Factor
' ScratchPad(8) : Mom Momentum Index
' ScratchPad(9) : RudMax.LowByte
' ScratchPad(10) : RudMax.HighByte
' ScratchPad(11) : Mode
' ScratchPad(12) : Bearing.LowByte
' ScratchPad(13) : Bearing.HighByte
' ScratchPad(14) : Speed
' ScratchPad(15) : Track.LowByte
' ScratchPad(16) : Track.HighByte
' ScratchPad(17) : TrackPrev.LowByte
' ScratchPad(18) : TrackPrev.HighByte
' ScratchPad(19) : omega.LowByte
' ScratchPad(20) : omega.HighByte
' ScratchPad(21) : omegaPrev.LowByte
' ScratchPad(22) : omegaPrev.HighByte
' ScratchPad(23) : SHelm.LowByte
' ScratchPad(24) : SHelm.HighByte
' ScratchPad(25) : RudPos.LowByte
' ScratchPad(26) : RudPos.HighByte
' ScratchPad(27) : cogreg i.e. 00011111 indicates cogs 0,1,2,3,4 are active
' ScratchPad(28) : startup
' ScratchPad(29) : err == 99 --> No NMEA data, reset needed
' ScratchPad(30) : unused
' ScratchPad(31) : unused
Upto index value 17 the BYTE and WORD are all zero.
For index value 17 and onwards I get the above stated values.
O.A.Ardali

Mike Green · 2010-01-12 19:08

You have a byte array. Don't use WORD to access it unless you know exactly what you're doing. WORD requires an address aligned on a word boundary which you don't have. In addition, the subscript field (WORD[noparse][[/noparse]<address>][noparse][[/noparse]<subscript>]) is in terms of words, not bytes. It's multiplied by 2 before adding the result to the address.

Post Edited (Mike Green) : 1/12/2010 7:13:12 PM GMT

O.A.A. · 2010-01-12 19:32

Thank you Mike.
I have overlooked the fact that the subscript field is in terms of words which of course causes an overflow outside the data block.
Thanks again.

SamMishal · 2010-01-12 19:34

O.A.A.

Change your code to Either

DAT
[b][color=red]    ScratchPad byte 0[noparse][[/noparse]32][/color][/b]
'                           0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1 
PUB Main 
   DIRA := %00001111_00000011_10100000_11111111 
   OUTA := %00000000_00000000_00000000_00000000 
   waitcnt(2_000_000 + cnt) 
[b][color=red]   workVariable := Byte[noparse][[/noparse]@ScratchPad][noparse][[/noparse]21] [/color][/b]
   If workVariable <> 0
     Beep
     Beep
PRI Beep
   repeat 2 
      !outa[noparse][[/noparse]Beeper]
      waitcnt(5_000_000 + cnt)

OR

DAT
[b][color=red]    ScratchPad Word 0[noparse][[/noparse]32][/color][/b]
'                           0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1 
PUB Main 
   DIRA := %00001111_00000011_10100000_11111111 
   OUTA := %00000000_00000000_00000000_00000000 
   waitcnt(2_000_000 + cnt) 
[b][color=red]   workVariable := Word[noparse][[/noparse]@ScratchPad][noparse][[/noparse]21] [/color][/b]
   If workVariable <> 0
     Beep
     Beep
PRI Beep
   repeat 2 
      !outa[noparse][[/noparse]Beeper]
      waitcnt(5_000_000 + cnt)

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Samuel

www.RobotBASIC.com
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