68300

Robert,
 
You might want to check how your compiler handles asm(" bset #3,$00FFFA15").
 
It might be better to type this   asm (" bset #3,($00fffa15).l ")
 
The ".l" forces long addressing which some compilers don't do unless forced to do.  Many compiliers default to ".w" instead of ".l".
 
 
 
Now, let's say that you held Data Bus 8 high at the release of reset.  This makes port E into bus control signals, including the RMC pin.
 
By default, the data direction register for Port E will contain $00.  
 
Now, you need to do two things.  1.  Make the bit in the Data Direction Register for RMC = 1, and change the bit in the Port E pin Assignment Register for RMC = 0.
 
Then, I think things will work.
 
Charlie
 

-----Original Message-----
From: Robert Manktelow [mailto:robert.manktelow@...]
Sent: Tuesday, January 07, 2003 4:02 AM
To: Yahoo 68300 group
Subject: [68300] Use of dual function Port E pin on the 68331


Hello All
Happy New Year to everybody.

Due to a shortage of bit output pins on our board I have tried using one of
the Dual function Port E pins ( either bus control pins or bit port pins) as
an bit output with conspicuous lack of success.
I wonder if this is a problem unique to me or not.

On page D19 of the User Manual the dual use of Port E is described. I have
used PEPA3 as a bit output (externally pulled high by a resistor) instead of
it driving the RMC bus control pin as we do not use this pin in the design.
I dropped into assembler as you can see. All is well initialising the port
as below:

// Set up PORT E, one bit of this controls the pSOS+ Interrupt Clock Source
PEPAR = PEPAR_SET ;  // Select the RMC pin only as a port, rest Bus Control
// Set the RMC / PE3 pin as a output, rest unchanged
asm(" bset #3,$00FFFA15") ;

However if I execute the next line the board crashes. It appears as if the
memory "disappears".
If I comment out the line below than the code runs on correctly.

// Set PE2 low, this enables the pip IRQ clock source. Pips will be coming
now.
    asm(" bclr #3,$00FFFA11") ;

Am I missing something here?
-
Robert Manktelow
Telspec Europe Ltd, Rochester, ME1 3QU
Phone +44 (0)1634 687 133 extension 2346



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