Hello List,

I have a little circuit which uses a PIC18F4320, whose Tx/Rx lines are tied 
together (Tx is connected through a diode, so it can only drive the bus 
low). It's very similar to the Parallax AppMods.

Now, any time I use putrsUSART(), it causes the DataRdyUSART() function to 
stop working. I attached the source code to this message. If you were to 
compile and run it as-is, and type "ABCDEFG" in HyperTerminal, you would 
see:

    AABBCCDDEEFFGG

However, if you were to uncomment the putrsUSART() function, you would get:

    Hello World!

    ABCDEFG

For some reason, after the putrsUSART() function is used, DataRdyUSART() 
never evaluates to TRUE.

A couple of observations:

1. Closing/opening the port after using the putrsUSART() fixes the problem.
2. putcUSART() does not have this issue.

I have a feeling that I am overlooking something very obvious. Any help with 
this matter is greatly appreciated!

Best regards,

Vitaliy

---------- Source Code -------------------

#include <p18f4320.h>
#include <delays.h>
#include <usart.h>

/* Set configuration bits for use with ICD2 / PICDEM2 PLUS Demo Board:
 *  - set HS-PLL oscillator
 *  - disable watchdog timer
 *  - disable low voltage programming
 *  - enable background debugging
 */

#pragma config OSC = HSPLL
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config DEBUG = ON

void main(void)
{
  char c;

   //Open the USART configured as 8N1 in polled mode
  OpenUSART (USART_TX_INT_OFF &
               USART_RX_INT_OFF &
               USART_ASYNCH_MODE &
               USART_EIGHT_BIT &
               USART_CONT_RX &
               USART_BRGH_LOW, 255);

  //putrsUSART((const far rom char *)"\rHello World!\r");

  while (BusyUSART()); // wait until transmission is complete

   for (;;)
   {
      if (DataRdyUSART())  // check USART read buffer
      {
         c = getcUSART();           // read character
         putcUSART(c);              // echo it back
         while (BusyUSART());       // wait until transmission is complete
         Delay1KTCYx(4);            // wait some more
         while (DataRdyUSART())     // empty the receive buffer
            getcUSART();
      }
   }
} 

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