It appears that perhaps the STATE variable is not being reset to 0 when  
receiving (or interactions of STATE with the Tx and Rx Ints).
 
Keep me in the loop.  It is probably something very simple.
 
 
 
 
In a message dated 5/13/2008 9:09:25 P.M. Central Daylight Time,  
namiller2@naxs.net writes:

Hi  everyone,

In the past, members of the list have been good at pointing  out programming
mistakes that I've made and I hope this time is no  different. :)

I'm trying to learn how to create a software UART which I  want to be
interrupt driven. I have a transmit routine that uses delay  loops written
and it works fine. My attempt at an interrupt driven transmit  doesn't work
and here is the symptom: no matter what is transmitted, 0xFE  is
received. The RS-232 parameters are 1200N1.

As a guide, the  interrupt driven routine is named "trasmit" and the relevant
labels in the  ISR are uart_3 and uart_4. The delay based routine is named
"transmit2" and  this routine works (Coding this was my fall back after
failing to get the  "transmit" routine to work.) The main loop sends a
sequence of bytes  starting with '!'.

I would be very grateful with being helped to  discover my mistake(s). The
program source code is attached.

BTW: I  found out the hard way that setting the OSCCAL value is very
important for  this kind of application!

Thanks!  Matthew

-- 
"With  reasonable men I will reason; with humane men I will plead; but to
tyrants  I will give no quarter."  -- William Lloyd


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