Agilent Technologies E5805A, Installation Manual

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10 E5805A USB/RS232 Interface
E5805A USB/RS232 Interface
When the Ignore Tx Purge flag is set the
SERIAL_PURGE_TXCLEAR command is ignored. The
function does not purge the write buffer.
• Disable Plug & Play : (Windows 2k/XP only)
Do not let the serial port enumerator detect devices plugged
into the 4 Port Interface.
• Timer Logic : (Windows 98SE only)
If the application uses PortSetReadCallBack(), the
notification routine is only 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 triggers
and calls 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for ~200ms (receiver is no longer active).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 E5805A USB/RS232 Interface’s buffering. However,
if you set the flag, the read is completed when ~200 ms of no
activity is detected.
Here is a comment from the code:
If the receiver is active, then do not complete this read. The
problem is that the device buffers the RX bytes and we poll
the driver. If we do not receive any bytes in 200ms we may
report an erroneous event even if there are available bytes
in the device or driver
.
Test Ports - Performs a confidence test on the internal
workings of the serial ports..