History RAM Data Capture Is Incomplete on PXIe‑6570

Issue Details

I am using the History RAM function to capture waveform data with a Visual Studio test program. The system uses a PXIe‑1083 chassis (integrated MXI) connected to a laptop.

The expected result is approximately 10.2k samples, as shown in the Digital Pattern Editor waveform capture. However, the data returned in the Visual Studio program is only approximately 8k samples.

Solution

This behavior is caused by streaming bandwidth limitations between the PXIe‑6570 and the host system.

The History RAM buffer refers to onboard memory on the PXIe‑6570 used to store captured results. The module guarantees storage of approximately 8k samples locally, regardless of system performance.

Capturing more than this amount requires streaming data from the module to the host system. The ability to retrieve additional samples depends on:

• System bandwidth (MXI link, bus utilization)
• Slot bandwidth and chassis configuration
• Other concurrent streaming operations

Because History RAM contains a large volume of data, streaming performance can limit how much data is successfully transferred to the host.

Upgrading system RAM does not improve this behavior, since the limitation is related to data transfer bandwidth, not host memory capacity.

Additional Information

One alternative is to configure History RAM to capture failures only. This reduces the amount of stored data, under the assumption that when a cycle does not fail, the expected and actual values match.