Hola, yo tengo el mismo problema, pero he encontrado en la ayuda del MPLAB un link
que me dice lo siguiente, y que la verdad no lo entiendo:
To use SCL Stimulus input to simulate USART/UART operation, follow the steps below.
Note: "Enable UART1 I/O" must be unchecked on the UART IO tab, Settings dialog (Debugger>Settings) or this method will not work.
Once the project is completed, you will need an input file to simulate USART signal input.
Select File>Open to open an editor window.
Enter data for RCREG input, i.e., values in column format. Example input might be:
10
20
34
Select File>Save and name the file input.txt.
Select Debugger>SCL Generator>New Workbook. Click on the Register Injection tab.
Under "Register", select "RCREG".
Under "Trigger", select "Demand".
Under "Data Filename", locate and select input.txt.
Under "Rewind", select "Yes".
Under "Format", select "Hex". You may select other formats, depending on the type of columnar data you entered in input.txt.
Click Generate SCL from Workbook and name the file usart.scl.
Click Exit and save the workbook (usart.sbs).
Select Debugger>Stimulus Controller>New Scenario.
Under "Stimulus (SCL) File", click Attach.
In the Open dialog, select usart.scl and click OK.
Click Save Scenario to save the scenario (usart.stc), then minimize this window as it must stay open for stimulus operation.
Open a Watch window to see the USART registers update.
Select View>Watch.
In the Watch window, add the SFRs RCREG and TXREG.
Build the project again and run it to see the output in the Watch window.
Select Project>Build All.
Place a breakpoint at the beginning of the interrrupt vector (IntVector) code, i.e., at line
"btfss PIR1,RCIF ; Did USART cause interrupt?".
Run the code till the breakpoint halt to see the value of RCREG change.
Step to see the value of TXREG change to match the injected value of RCREG.
Run and step again to see the values change as per the input file.
