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Overrun and Overflow Errors

As a software-based product, the speed of your computer's processor affects FTS's performance. Overrun errors and buffer overflows are indicators that FTS is unable to keep up with the data. The information below describes what happens to the data as it comes in the port, what the two types of errors mean, and how various aspects of FTS affect performance. Also included are suggestions on how to improve performance.

Data captured by the serial port first goes into the buffer of the UART chip of the serial port. The UART generates an interrupt, which tells the FTS driver to check the port. The driver takes the data from the UART and counts each byte as they are put into the driver's own buffer. The driver tells FTS that data is ready to be processed. FTS takes the data from the driver's buffer and puts the data into the capture buffer.

Overrun errors occur when the data in the buffer of the UART is not retrieved before new data comes in. In this case, FTS knows that it has lost information but it does not know how much. FTS indicates overrun errors in the Event Display screen by marking a byte near the overrun in red. You can search for overrun errors using the Find feature.

If you are experiencing Driver Buffer Overflows, go to Options | System Settings and click on the Advanced button.  Increase the Driver Receive Buffer Size (the default setting is 8) to about 100, then try capturing again.  If the overruns persist, keep increasing the buffer setting until they are gone.  If this doesn't solve the problem, you may need a faster PC.