jump to the wrong page

paolo · 2008-03-17 09:29

Hello,

I'm having a very strange problem with the SX48.
I'll try to explain what's happening:

The chip is used to control a disc loading robot with two DC motors, one solenoid and four optical sensors.
The program is written in SXB, and uses a small time-based ISR written in assembler.

Here is the description of the problem:

The program uses a subroutine (MoveToPosition_Y) that moves vertically the loading arm until it reaches certain position.
This subroutine calls the "Move_V" subroutine which gives power to the motor and programs a timer in PWM mode for the speed control.
The problem is that "Move_V"· is never called from the MoveToPosition_Y sub.

Using the debugger, I've inserted a break-point in the·compiler generated code where the jump to the actual address of Move_V is coded.
I've attached a picture that shows the status of the registers as soon as the break-point pops up.
As you can see, the last executed instruction should be "PAGE 800", but the STATUS register does not have the correct value, and points instead to a wrong page.
As a result, the following jump instruction loads the PC with the wrong address.

The strange thing is that if I insert a NOP at any point in the code before calling the Move_V sub, the program works perfectly.

I'm really getting crazy because I cannot find out the cause of this strange behavior.

I'm using the SX-Key ver. 3.2
SASM DLL ver. 1.51.07
SX-B ver. 1.51.03
SXSim ver. 2.08.05

Does anybody have an idea?
I can post the full source code if needed.

Thank you.

Bean · 2008-03-17 11:35

Please post the source code.

Are you calling Move_V from assembly or from SX/B ?

Bean

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·

paolo · 2008-03-17 11:38

Hi Bean,

Move_V is called from SX/B

paolo · 2008-03-17 11:39

Here is the source code

Bean · 2008-03-17 12:37

I don't know if this is what is causing the problem, but you should use "SUB Move_V" and "ENDSUB".
Instead of :

Move_V: 'USES: Temp1
 Moveing_V = 1
 if toUp = 1 then
  Down_Move = 0
  Up_Move = 1
 else
  Up_Move = 0
  Down_Move = 1  
 endif
 SetPower 'temp1
 return

You should have:

SUB Move_V 'USES: Temp1 (note NO colon)
 Moveing_V = 1
 if toUp = 1 then
  Down_Move = 0
  Up_Move = 1
 else
  Up_Move = 0
  Down_Move = 1  
 endif
 SetPower 'temp1
ENDSUB

All of your SUBs and FUNCs should be this way. This let's the compiler understand that this is a subroutine and not just part of the main code.

Change these and see if that fixes the problem.

Bean.

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·

paolo · 2008-03-17 15:00

Thank you Bean for your suggestion.

I've changed the code with SUB/FUNC·- ENDSUB/ENDFUNC and·the program·has started to work fine.

BUT: I've looked at the list and I've found that the new address of the·subroutine·MoveToPosition_Y was 80C, while in the·previous version·of the program the subroutine was located at address 808.
I've then removed a couple of instructions at the beginning of the program in order to·have this subroutine·located at the same address of the previous not-working version.
I've tested this new version and... it didn't work!
The problem is still the same: the PAGE instruction does not seem to correctly set·the page bits in the·status register·before jumping to·the Move_V subroutine.

Note that Move_V·works fine when called from subroutins others than MoveToPosition_Y.

I've attached this new version of the program.

Thank you.
Paolo

paolo · 2008-03-17 17:22

Hi,
I've probably found the problem.
I've changed the frequency from 20Mhz to 50Mhz and the program started to work.
I suspect there's some noise problem with the layout of the board.

Thank you for the time you have spent on this issue.

Paolo

jump to the wrong page

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