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Multiplexer Driver Developer’s Guide

2.4 Handling of Control Lines on Virtual Ports

Mux_Drv_DevGuide_v07 Page 14 of 36 2006-9-27

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2.4 Handling of Control Lines on Virtual Ports

Summary of control line handling.

2.5 Limitation of Virtual Ports

Flow control can be set to RTS/CTS or DSR/DTR. XON/XOFF flow control is not supported. Hardware flow con-

trol on the virtual COM ports is handled internally by the Multiplexer Protocol.

The WinMux2k driver handles neither modem nor serenum IO-control requests.

The WinMux2k driver supports only 8 data bits, no parity, and one stop bit.

The function IOCTL_SERIAL_XOFF_COUNTER is not supported.

The following functions return “success”, but have no effect at all:

• IOCTL_SERIAL_SET_BREAK_ON

• IOCTL_SERIAL_SET_BREAK_OFF

• IOCTL_SERIAL_SET_XOFF

• IOCTL_SERIAL_SET_XON

• IOCTL_SERIAL_RESET_DEVICE

Virtual ports accept any baud rate, though the changed setting will be ignored. Calling the function Open() to a

virtual port can take up to 40 seconds. It fails if the module is not connected.

Table 2: Virtual serial port with Multiplexer Protocol version 2

Signal Description

RING Read from hardware port, distributed to the first virtual port

DCD Read from hardware port, distributed to the first virtual port

DSR Received with Modem Status Command

DTR Set by user, sent with Modem Status Command, initialized with 1

CTS Received with Modem Status Command

RTS Set by user, sent with Modem Status Command, initialized with 1

Table 3: Virtual serial port with Multiplexer Protocol version 3

Signal Description

RING Received with Modem Status Command

DCD Received with Modem Status Command

DSR Received with Modem Status Command

DTR Set by user, sent with Modem Status Command, initialized with 1

CTS Received with Modem Status Command

RTS Set by user, Send with Modem Status Command, initialized with 1

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