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Newsgroups: comp.os.msdos.djgpp
Subject: Re: An interrupt drived uart program dead
Date: Thu, 21 May 2009 06:49:07 -0700 (PDT)
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

The bug is found. Rod Pemberton is right. The do-while loop in the
commISR never exits. I miss a "break" statement after "txIdle = true;"
in the do-while loop. the correct code block is follow:
-------------------------------------------------------------------------------------------------------------------------------
     do {
         if (queueSize > 0)
         {
            byte data = writeQueue[queueHead];
            queueHead = (queueHead + 1) % QUEUE_CAPABILITY;
            queueSize --;
            outportb(baseAddress + OFFSET_THR, data);
            txIdle = false;
         }
         else
         {
            txIdle = true;
            break;             // this statement missed so can't exit
the do-while loop.
         }
         lsr = inportb(baseAddress + OFFSET_LSR);
      } while((lsr & (LSR_THRE | LSR_TEMT)) != 0);
-------------------------------------------------------------------------------------------------------------------------------

Very thanks for everybody's help. All suggestion give me the good idea
for the future develop in DOS.
God bless you all ! :-D