Tool/software:
The program I am working on has the desire to optionally connect adjacent VPX slots via 4-channel PCIe across the backplane, so the device is being used as a software controlled connect/disconnect rather than a mux. To implement this, I have two instances of the 4412 part connected as follows, with the Tx’s and Rx’s of each slot connected to the same pins on each device
- I want to make sure this configuration will work as expected, as well as discuss the behavior of the input (DA) and output (D) pins when the device is in standby mode. The initial idea was to tie the select pin low (DA) with hardware and toggle power down pin with software to enable to passthrough, however I can bring a control pin to both Select and PD if needed, as shown below.
- The assumption is each daughtercard will have blocking caps on the TX line, however the caps shown below are still installed on the backplane as precautionary. The datasheet mentioned biasing to CMV if using caps on both sides of the Mux. I do not have caps on the D-side, but I am wondering if the intent for biasing is if there are consecutive caps on the channel between the two endpoints, Daughtercard X and Y. If so, is it best to add biasing, remove the extra cap? I have also heard consecutive caps is not ideal but performance should not be affected so perhaps there is no change necessary.
