Configure Serial Ports

You can adjust baud rate, protocol, flow control, and hardware handshaking for serial ports on devices that support these settings.

You should use the fastest available baud rate and the protocol recommended by your device manufacturer. See the documentation that accompanies your device.

NoteThe settings on your plotter must match the settings in AutoCAD or you will not be able to plot.

Flow Control and Handshaking

Your computer can produce a plot file faster than most plotters can process it. Plotters have a limited amount of memory and as this memory fills up, the plotter must be able to tell your computer to stop sending data temporarily. Then, when plotter memory is freed up as the plot is processed, the plotter must be able to tell the computer to resume sending the plot file. This communication is called flow control or handshaking.

There are two methods of handshaking: hardware and software. Hardware handshaking uses additional wires in the cable between the plotter and computer. These wires are dedicated to handshaking signals or on/off voltages. Software handshaking uses a single wire to send streams of commands that include start/stop handshaking signals. The most common type of software handshaking is XON/XOFF. You must provide different cables for hardware and software handshaking.

Procedure

To adjust serial port settings

From the File menu, choose Plotter Manager.
Double-click the plotter configuration (PC3) file whose serial port settings you want to change.
In the Plotter Configuration Editor, choose the Ports tab and select the serial port that you want to use.
Choose Configure Port.
In the Settings for COM Port dialog box, select a baud rate and protocol for your device.
The protocol settings available for the current device are displayed. You cannot set an invalid protocol.
Select a Flow Control method.
The default flow control setting is XON/XOFF (software handshaking) for compatibility with previous versions of AutoCAD. If you select Hardware handshaking, you can specify additional settings by choosing Advanced.

In the Advanced Settings for COM Port dialog box, the following settings correspond to different pins on the serial port:
- CTS. Enables Clear to Send handshaking. This monitors pin 5 of a 25-pin serial port or pin 8 of a 9-pin serial port. CTS is an input bit, monitored for an output from the plotter or printer.
- DSR. Enables Data Set Ready handshaking. This monitors pin 6 of a 25-pin serial port, or pin 6 of a 9-pin serial port. DSR is an input bit, monitored for an output from the printer or plotter.
- RLSD. Enables Received Line Signal Detector handshaking. This is sometimes called Data Carrier Detect or DCD. It's an input pin that can be monitored for an output from the plotter. It's on pin 8 of a 25-pin serial port and on pin 1 of a 9-pin serial port.
- RTS. Controls the Request to Send output bit. This sends a signal to the printer or plotter on pin 4 of a 25-pin serial port or on pin 7 of a 9-pin serial port.
  Disabled. Disables the RTS line when the device is opened.
  
  Enabled. Enables the RTS line when the device is opened.
  
  Handshake.Enables RTS handshaking. The driver raises the RTS line when the “type-ahead” (input) buffer is less than one-half full and lowers the RTS line when the buffer is more than three-quarters full.
  
  Toggle. Specifies that the RTS line will be high if bytes are available for transmission. After all buffered bytes have been sent, the RTS line will be low.
- DTR. Controls the Data Terminal Ready output pin. This sends a signal to the printer or plotter on pin 20 of a 25-pin serial port or on pin 4 of a 9-pin serial port.
  Disabled. Disables the DTR line when the device is opened.
  
  Enabled. Enables the DTR line when the device is opened.
  
  Handshake. Enables DTR handshaking.
Choose OK to close the Advanced Settings for COM Port dialog box. Choose OK to close the Settings for COM Port dialog box.

Quick Reference

Commands