From: terje.mathisen@nospicedham.tmsw.no   
      
   Paul Edwards wrote:   
   > On Saturday, April 15, 2023 at 10:36:37 PM UTC+8, Paul Edwards wrote:   
   >   
   >> I finally realized that since I'm getting an interrupt from   
   >> the TBE enable (for unknown reasons), then if I moved   
   >> the disable (cli) before that, then by the time I had   
   >> outputted a byte, the interrupt would still be pending   
   >> and even if I didn't get one for the outputted byte, it   
   >> was enough to get one for the TBE call.   
   >>   
   >> And now it is working, with the simple design.   
   >   
   > Note that it is working (and previously failing) under   
   > Bochs. I haven't tried real hardware yet.   
   >   
   > And now I realize there may be a problem with the   
   > current code.   
   >   
   > Let's say the serial port is slow.   
   >   
   > The sequence I am doing is enabling TBE and then outputting   
   > a byte.   
   >   
   > Enabling TBE generates an interrupt, but outputting the byte   
   > only randomly does (could also be a Bochs bug).   
   >   
   > Because I am now relying on the TBE enable interrupt to get   
   > me out of the HLT loop, I am no longer have the desired   
   > constraint on the OUT instruction completing.   
   >   
   > Meaning the second time through the loop, the second OUT   
   > could be executed before the first one has completed.   
   >   
   > If the UART discards the TBE interrupt when it realizes that   
   > it is no longer the case that the transmit buffer is empty,   
   > because there has been an OUT instruction issued since   
   > then, then my current design should work.   
   >   
   > Does anyone know what is happening?   
   >   
   > Thanks. Paul.   
   >   
   How do you guarantee that the interrupt is directed to your thread   
   that's sitting in a HLT state?   
      
   Terje   
      
   --   
   -    
   "almost all programming can be viewed as an exercise in caching"   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)