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Peripheral Simulation

For Handshake Solutions HT80C51 — Serial UART

Simulation support for this peripheral or feature is comprised of:

  • VTREGs (Virtual Target Registers) which support I/O with the peripheral.

These simulation capabilities are described below.

Data Type: unsigned int

The SIN VTREG represents the serial input of the simulated microcontroller. Values you assign to SIN are input to the serial channel. You may assign input using the command window. For example,


causes the simulated microcontroller serial input to receive the ASCII character A. If you want to use the SIN VRTEG to simulate reception of multiple characters, you must be sure to delay for atleast one character time between successive assignments to SIN. This may be done using a signal function. For example:

signal void send_cat (void) {
swatch(0.01);  /* Wait 1/100 seconds */
SIN='C';       /* Send a C */

You may use the SIN VTREG to input more than 8 bits of data. For example,


inputs a 9-bit value. This is useful if you use 9-bit serial I/O. In addition to the SIN VRTEG, the serial window allows you to input serial characters by simply typing. Serial characters that are transmitted byt the simulated microcontroller appear in the serial window.

Data Type: unsigned int

The SOUT VTREG represents the serial output from the simulated microcontroller. Whenever the simulated serial port transmits a character, the value transmitted is automatically assigned to SOUT (which is read-only). You may read the value of SOUT to determine the character transmitted by your simulated program. For example,


outputs the value of the last character transmitted. You may use the SOUT VTREG in a script to process transmitted data. For example,

signal void sout_sig (void) {
while (1)
  wwatch(SOUT);     /* wait for something in SOUT */
  printf ("Transmitted a %2.2X\n", (unsigned) SOUT);

Data Type: unsigned char

The STIME VTREG allows you to control the timing of the simulated serial port.

  • A value of 1 (which is the default) indicates that the serial port timing is identical to the target hardware. Use this value when you want to see the effects of baud rate on the serial port I/O.
  • A value of 0 indicates that all serial input and output occur instantaneously. Use this value when you don't care about any baud rate effects or when you want serial output to be fast.

For example:

STIME = 0   /* Set Serial Port for FAST timing */
STIME = 1   /* Set Serial Port for accurate timing */
Get more information about the
Peripheral Simulation Capabilities
of the µVision Debugger.
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