Problems with const array of functionpointers (p16 only?)

[Dany]

v.5.6.1.

Hi, during testing on a P16F628A of the "StateMachine library" I encountered a peculiar phenomenon: the execution of the last entry in a "const array" of "pointers to functions" failed: the PIC resets.

In the code below I would expect an output (via uart) as here:

Started
From: 0, To: 2, Event: 3
From: 1, To: 2, Event: 3
From: 2, To: 2, Event: 3here

but I see

Started
From: 0, To: 2, Event: 3
From: 1, To: 2, Event: 3
Started <--- reset
From: 0, To: 2, Event: 3
From: 1, To: 2, Event: 3
Started <--- reset
From: 0, To: 2, Event: 3
From: 1, To: 2, Event: 3
Started <--- reset
etc...

Apparently when the last entry in the array gets executed something goes wrong, the PIC restarts.

This is the code:

Code: Select all

{$DEFINE DEBUG}

type TActionProc = procedure(From, Towards, Event: byte);

Procedure A_a(from, towards, event: byte);
begin
  {$IFDEF DEBUG} ShowAction(From, Towards, Event); {$ENDIF}  
end;

Procedure A_b(from, towards, event: byte);
begin
  {$IFDEF DEBUG} ShowAction(From, Towards, Event); {$ENDIF}  
end;

Procedure A_i_(from, towards, event: byte);
begin
  {$IFDEF DEBUG} ShowAction(From, Towards, Event); {$ENDIF}  
  Uart_write_Line('here');
end;

const SmallTable: array[3] of ^TActionProc =
      (@A_a,
       @A_b,
       @A_i_
      );
....
begin
  { Main program }

  CMCON  := 7;             // Disable Comparator module's
  PORTA  := 0;             // initialize portA
  TRISA  := %00110011;
  
{$IFDEF DEBUG}
  Uart1_init(9600);
  delay_ms(100);
  Uart_write_Line('Started');

  for TmpIndex := 0 to 2 do
  begin 
    SmallTable[TmpIndex]^(TmpIndex, 2, 3);  // call the routine, first parameter is the index in the table
    Uart_write_line('');
  end;
  Uart_write_line('');
  
  while true do ;
{$ENDIF}
end.

As you can see the only action done here is to call (indirectly) all entries in the table "SmallTable".

Only the last entry in the table shows the erroneous behaviour, so extending the table with one (not used) entry (e.g. with "nil" as value) makes the problem go away.

I have only see this with the P16F628A, not with e.g the P18F2550.

As far as I can tell the content in rom of "SmallTable" seems to be correct (tough I do not understand it).

Thanks in advance!

[Dany]

Hi mE people, were you able to reproduce this phenomenon?

Thanks in advance.

[janko.kaljevic]

Hello Dany,

I apologize for the late reply.

I was able to reproduce this behavior on PIC16f controllers, and we will work on this issue.
As you have noticed at the moment, workaround is to use larger array for one element.

I will notice you, regarding our findings.

Best regards.