Keysight Technologies M5302A Startup Manual page 19

Overview on M5302A PXIe LVDS Digital IO Modules 1
Figure 3 M5302x SFP controls for the 100-pin LVDS connector
All user LVDS lines run from the FPGA to the LVDS connector. Samtec
cable is 50-ohm coax, single-ended. Differential pairs are run at 100-ohm
differential on the board. Grounds between pairs are run as individual coax
(center pins). This is needed for direct-connect boards (with no cable).
Ground of coax shields connects to latches and PMH pins.
The LVDS_TXDISABLEn_OUT / LVDS_TXDISABLEn_IN controls in Figure 2
provide M5302A module output protection by allowing control over the
transmission of LVDS signals in and out of the module. These are
controlled by the "DifferentialChannels.OutputSafetyState()" API in the
M5302x software or the Protection Enabled check box in the M5302x SFP,
as shown in Figure 3.By default, the LVDS_TXDISABLEn_OUT is driven
high anytime the module is powered on and the FPGA is configured. The
LVDS_TXDISABLEn_IN line must be manually driven high before the
M5302A module attempts to drive any of the LVDS channels that are
configured as outputs unless you override this condition by setting the
DifferentialChannels.OutputSafetyState() API to 'Disabled'.
When driving high, make sure to set LVDS_TXDISABLEn_IN to +3.3V
through a 5K resistor.
M5302A PXIe LVDS Digital IO Modules Startup Guide 19