_VCOMM_EscapeCommFunction

include vcomm.inc

VxDCall _VCOMM_EscapeCommFunction, <hPort, lFunc, \
    InData, <OFFSET32 OutData>>
or      eax, eax
jz      error_handler

Directs the communications port driver to carry out an extended function. Uses the C calling convention. This is an asynchronous service.

Returns TRUE if successful, FALSE otherwise. For extended error information, use _VCOMM_GetLastError.

hPort

Handle of a communications resource.

lFunc

Value identifying the extended function to carry out. The following common extended functions are defined in VCOMM.INC.

Value	Meaning
CLEARBREAK	Clears break condition, resuming transmission.
CLRDTR	Clears the DTR signal.
CLRRTS	Clears the RTS signal.
DUMMY	Performs no action.
GETCLOSEPROP	Returns the close property of the port driver in the address specified by the OutData parameter.
RESET	Asserts a signal on the reset line of an LPT port, if available. This can be used to reset a printer. No action is taken if the hPort parameter identifies a COM port.
SETBREAK	Sets the break condition, halting transmission.
SETCLOSEPROP	Sets the close property of the port driver to the InData parameter. The previous close property is returned in the address specified by the OutData parameter.
SETDTR	Sets the DTR signal.
SETRTS	Sets the RTS signal.
SETXOFF	Causes transmission to act as if an XOFF character has been received.
SETXON	Causes transmission to act as if an XON character has been received.

Port drivers can define additional extended functions to expose device-specific features. Extended functions can be used in conjunction with driver-defined events to facilitate two-way message passing between an application and port driver.

InData

Function-specific 32-bit parameter.

OutData

Address to receive function-specific data.

Except for GETCLOSEPROP and SETCLOSEPROP, the extended functions defined in VCOMM.INC ignore the InData and OutData parameters.

_VCOMM_EscapeCommFunction

See Also