For a project, I am using a USB-7845 Multifunction Reconfigurable I/O Device connected by a SHC68-68-RMIO wire to an SCB-68a terminal block to output 4 discrete lines. The RMIO is connect to the HSDIO port of the Multifunction I/O (connector 0) and I have been able to output pulses on an 80Mhz clock schedule. The SHC68-68-C68-RDIO2 and the SCB-68 are built for HSDIO but you can not solder any add-ons to the the SCB-68 terminal block like you can for the SCB-68a which is preferred for my project. Is there any reason why I shouldn't connect the RMIO and 68a to the HSDIO port of the FPGA? am I in danger of damaging my equipment?
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I would say - yes, you might damage your device.
The reason is that these special cables RMIO and RDIO2 have different cable pairings and ground wire mappings when used for a different use case will short an actual channel to ground.
Trust me, found the wrong way, recently after a week-long debug found that we were using SHC68-C68-D4 VHDCI-VHDCI cable with 673x AO which is incompatible since the D4 version grounds every alternate pin as how the connector pinout of HSDIO/657x is mapped but when used with a DAQ, it shorted out active AO channels to ground.
Go with the recommended cables and do not change, if you still want to be sure, get the specification (or drawing) for the cables and you can see the wire mappings.
Hmmm... then I will try to use the 68 with the RDIO on connector 0. would you have any idea how to solder a RS-422 chip on the 68? I was looking up the users manual for soldering onto the the actual terminal block but it was no help. I have no clue what the 5 shield holes next to each pin are connected to.
Those are for soldering SMB connectors, the centre pin connects to the signal and 4 pins in the corners are just GND.
Centre signal is labelled on the board as in the below image,
No, you cannot directly solder RS-422 chip in the SCB-68 for HSDIO, you have to wire them to a separate board from this terminal block. SMB connector locations are available to wire external equipment preserving signal integrity at high frequencies 10MHz+