Visa Lastbit setting controls which bit?

[Cherry68]

Using Measurement Studio Visa to control a serial port for a custom packet protocol I would like to use LastBit termination - which bit is set/cleared i.e. what is considered the last bit. Comport=19200,n,8,1
*Is the stop bit used as the last bit??
thanks

[Dan_Mondrik]

Cherry:

The last-bit and the stop-bit are 2 different things. The last-bit VISA setting lets you basically treat an extra out-of-band data-bit as an EOI character. Some devices may send back the last byte of data with the most significant bit set. So for example, a linefeed without EOI would be 0x0A, as you expect, but a linefeed signifying EOI would be 0x8A.

The stop-bit is a lower level serial thing.

The last-bit setting is not something that a whole lot of devices use, but I do know that they exist.

Also, if you will use this setting, I suggest you use NI-VISA 2.5 because there were some bugs fixed related to the last-bit feature.

Dan Mondrik
Senior Software Engineer, VISA
National Instruments

[Cherry68]

I am working with a "binary" protocol which has messages that vary in length - How can I trap end-of-message? Also, why dose VISA endin not support Break as EndOut dose? This could have worked for me.
Thanks again.