More Settings Serial Port Dialog Box

NOTE:Modem pacing is set from the More Settings - Modem dialog box.


It is possible for Reflection to transmit data to a serial device faster than the device can process it, or for a serial device to transmit data to Reflection faster than Reflection can process it.

Should this continue for too long, the slower system's buffer overflows and data is lost. If the serial device recognizes the XON/XOFF handshake, you can prevent the buffer from overflowing by keeping this value set to Xon/Xoff.

Xon/Xoff transmit pacing works as follows:

  • When the receive buffer has a limited amount of space left, an XOFF (DC3) character is sent as a signal to stop transmitting.

  • After processing most of the backlog of characters in the receive buffer, an XON (DC1) character is sent as a signal to resume transmission.

    The two systems continue in this stop-and-go fashion until all the data has been transmitted.

    If Hardware is selected, the RTS and CTS pins on the RS-232 serial cable control data flow.

    When both the Receive and Transmit options under Pacing are set to None and you're emulating a VT series terminal, Hold Session (VtF1) has no effect.


Select a flow control method to use when Reflection transmits data to a serial device on this port.


Select a flow control method to use when the serial device on this port transmits data to Reflection.

Char transmit delay

It is possible for Reflection to send data to the host faster than the host can receive it. For example, if you paste text from the Clipboard into a host editor such as EDT, you may overrun the host's buffer.

By setting a delay between characters, you can specify how long Reflection should wait after each character when transmitting blocks of characters to the host.

This delay also affects character transmission during file transfers. Setting a value of 3 at 9600 baud lowers the effective speed of data transmission to about 2400 bits per second.

On a VMS host, setting the terminal's HOSTSYNC characteristic can also help prevent overrunning the host's buffer when pasting data. To do this, enter the following command at the DCL prompt: SET TERMINAL/HOSTSYNC.

For backward compatibility, you can enter a value for character delay of up to 255. However, the maximum in Reflection always reverts to 100.

Line transmit delay

Set the amount of time Reflection should wait after transmitting a carriage return character (the line delimiter) before transmitting the next line.

This setting also affects the delay between frames during file transfer using the WRQ/Reflection protocol. Assigning a delay may help if you are experiencing file transfer problems over an X.25 connection.

Use threaded I/O

Select to send communication calls to an independent thread that handles IO (Input/Output) processing, thus improving performance.