## Physical Device Driver Reference

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### ASYNC_EXTSETBAUDRATE (43h) - Bit Rate

Bit Rate The Bit Rate field is a binary integer representing the actual bit rate (bits-per-second) that the physical device driver uses to set the bit rate of the COM device. For a COM port that is supported by Enhanced UART or compatible serial communication devices, the range is 10 bps - 345600 bps. The user can get the minimum and maximum bit rates supported by the physical device driver on a COM port by using "Function 63h - Extended Query Bit Rate".

Note:

Due to system overhead and the physical limits on the hardware cables, actual bit rates might be restricted.

When this function is used for a COM port that has no support of the Enhanced UART or compatibles, then the bit range supported by the device driver is from 2 bps - 19200 bps. A call with a bit rate out of range fails with the ERROR_INVALID_PARAMETER return code.