## Physical Device Driver Reference

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### ASYNC_SETMODEMCTRL (46h) - COM Error WORD (COMERR)

COM Error WORD (COMERR) The physical device driver returns this information if a general failure error is not returned to the application. See the ASYNC_GETCOMMERROR for COMERR definition. The COM device error information is not cleared by this action. At device driver initialization, the device driver turns off DTR and RTS for the COM devices that it owns.

When the COM device is not already open (from a previous Open without a Close), the OPEN request packet causes DTR and RTS to be set according to the DTR Control mode and the RTS Control mode. See Note 1 of ASYNC_ SETDCBINFO.

Note: If the port will not be open after processing a CLOSE request packet (Last Level Close), DTR and RTS are turned off by the device driver. This occurs after the transmit hardware has completely transmitted (at the physical RS232 interface) all the data that it has been given by the physical device driver and time for at least 10 additional character transmissions has elapsed.