IMAQ IMG_ATTR_LAST_VALID_FRAME overflow

[BartSteinmayr]

Everyone,

I am not sure if this is the correct forum for IMAQ C questions, please move this thread if necessary.

We are using NI-IMAQ 18.0 and a 1433 PCIe framegrabber to read data from a line camera.
When querying IMG_ATTR_LAST_VALID_FRAME using the GetAttribute call, we get the expected results, but after 28 bits (i.e. 

roughly 268435455 frames), the value wraps around to 0. This is unexpected (since the value is an uInt32), undocumented and has caused systems to fail at our customers.

We would therefore like to know if this 28-bit restriction applies to all NI framegrabbers and software versions and what exactly the range of the value is. Is 2^28-1 the highest value ever returned from the function?

Thank you and best regards,
Bart

[bhovhann]

Hi,

The basis for the Camera Link standard is the National Semiconductor
Channel Link chipset, a data transmission method consisting of a
general-purpose transmitter/receiver pair. The Channel Link driver takes
28 bits of parallel digital data and a clock and serializes the stream to
four LVDS (EIA-644) data streams and an LVDS clock, providing
high-speed data transmission across 10 wires and over distances of
up to 10 m.

Useful links

NI Framegrabber Specifications for the NI Camera File Generator

https://www.ni.com/en-us/support/documentation/supplemental/18/framegrabber-specifications-for-the-n...