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USB Plus Series Installation Guide (90000410 Rev. C) – Page 9
Low Latency:
Normally the UART will interrupt when the receiver has been idle for 4 character times.
(For example 4ms at 9600) As long as data is being received the UART will continue to
buffer them until its internal FIFO is full (~56 bytes). This flag causes the Edgeport to
poll the RX FIFO for received bytes. If any bytes are available they will be sent to the
driver without any delay.
Remap Baud: (All operating systems)
Setting the baud rate to 1200 baud will result in 230400 baud
Ignore Flush: (Windows NT/2K/XP)
If an application sends IRP_MJ_FLUSH_BUFFERS it will be ignored.
Excerpt from Microsoft documentation:
Drivers of devices with internal caches for data and drivers that maintain internal buffers
for data must handle this request.
When Sent
Receipt of a flush request indicates that the driver should flush the device's cache or its
internal buffer, or, possibly, should discard the data in its internal buffer.
Operation
The driver transfers any data currently cached in the device or held in the driver's internal
buffer(s) before completing the flush request. The driver of an input-only device that
buffers data internally might simply discard the currently buffered device data before
completing the flush IRP, depending on the nature of its device.
Fast Writes: (All operating systems)
When an application sends a write to the driver, by default the Edgeport driver will wait
until all data has been transmitted out of the Edgeport device before completing the write.
When the Fast Writes flag is set, we complete the write even if data is still buffered in the
driver and the Edgeport device.
Fast Reads:
This flag is used when an application requires that a read complete immediately. In the
read immediate case, the Edgeport driver will send a request to the Edgeport device
asking for any buffered data to be sent up. This buffered data will be included when the
read completes. If this flag is set, the driver will not query the Edgeport device for
additional data.
Timer Logic: (Windows 9x only)
If application uses PortSetReadCallBack(), the notification routine will only be called
when the number of bytes in the receive buffer is greater then the RX trigger. The
Microsoft serial VxD also implements a timer that will trigger and call the notification
routine if some amount of data is
available in the RX buffer but no new data has been
received for ~200ms (receiver is no longer active).
We do not enable this behavior by default because of the nature of Edgeport buffering.