Technical Support

µVISION DEBUGGER: USING THE PORTX VTREGS

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Information in this article applies to:

• C166 All Versions
• C251 All Versions
• C51 All Versions
• CARM All Versions
• µVision Version 2

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QUESTION

What is the PORT0/PORT1/PORT2/... VTReg and how do I use it?

ANSWER

The Keil µVision Simulator provides Virtual Target Registers (VTRegs) to support input to the I/O pins of the simulated device.

The PORTx VTRegs represent the inputs to the pins of the MCU for Port 0, Port1, Port2, and so on.

So, if you have configured an I/O port for input, the following commands (typed in the debugger's Command Window) may be used to set and then clear bits of an I/O port (bit 7 of port 3 in this example).

PORT3 |=  0x80  /* Set P3.7 */
PORT3 &= ~0x80  /* Clear P3.7 */

You may create signal functions that toggle port pins periodically, simulating a pulse train. For example:

signal void P3_toggles (void) {
  while (1) {
    PORT3 ^= 0x80;
    swatch (0.500);  /* wait for 1/2 a second */
  }
}

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The following example shows how you can monitor the state of 2 port pins:

#include <reg167.h>
#include <stdio.h>

void main (void)
{
/*---------------------------------------------------------
Setup the serial port
---------------------------------------------------------*/

  P3  |= 0x0400;        /* SET PORT 3.10 OUTPUT LATCH (TXD)              */
  DP3 |= 0x0400;        /* SET PORT 3.10 DIRECTION CONTROL (TXD OUTPUT)  */
  DP3 &= 0xF7FF;        /* RESET PORT 3.11 DIRECTION CONTROL (RXD INPUT) */
  S0TIC = 0x80;         /* SET TRANSMIT INTERRUPT FLAG                   */
  S0RIC = 0x00;         /* DELETE RECEIVE INTERRUPT FLAG                 */
  S0BG  = 0x40;         /* SET BAUDRATE TO 9600 BAUD                     */
  S0CON = 0x8011;       /* SET SERIAL MODE                               */

/*---------------------------------------------------------
Setup Port 0H (bits 3 and 4) for Input
---------------------------------------------------------*/
DP0H &= ~((1 << 3) | (1 << 4));

/*---------------------------------------------------------
Read Port 0H.3 and 0H.4 and output the value
---------------------------------------------------------*/
while (1)
  {
  printf ("P0H.3 = %s  P0H.4 = %s\n",
          ((P0H & (1 << 3)) ? "HI" : "LO"),
          ((P0H & (1 << 4)) ? "HI" : "LO"));
  }
}

SEE ALSO

• µVision DEBUGGER: USING THE AINX VTREGS
• µVision DEBUGGER: USING THE STIME VTREG
• µVision DEBUGGER: USING THE SIN VTREG
• µVision DEBUGGER: PORT LINES DON'T TOGGLE DURING MEMORY ACCE
• µVision DEBUGGER: I/O PINS DON'T TOGGLE DURING COMMUNICATION

FORUM THREADS

The following Discussion Forum threads may provide information related to this topic.

• Reading values from I/O port
• How to simulate a input?

Last Reviewed: Tuesday, May 03, 2005

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