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MCC USB-DIO24/37: pull pins down?



Hello - 

I use the MCC USB-DIO24/37 in an OEM application. I have an issue where I'd like to pull some pins down to ground, but I'm not really sure how this is intended to be done. From the User's Guide: 


Pull up/pull-down configuration: All pins pulled up to Vs via 47 kΩ resistors (default). Selection available for pull down to ground. Hardware selectable via zero Ω resistor.

It's not clear to me how I can identify the selection that is available for pull down, or where I need to adjust the hardware to enact this change. Does anybody know how this might be done? Would this be a global change, or is this selectable for some pins only? 



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Hello @aelsey.

On the MCC USB-DIO24/37 PCB silkscreen, you should find the RN1, RN3, and RN5 locations for the 47 kOhm resistor networks.  Adjacent to each resistor network, you should also find 0 Ohm resistors (R69, R70, and R71) soldered to the HI spots.  A user would move the 0 Ohm resistor to the LO spot in order to change them to pull-down resistors.  (Digilent does not provide a service to make this change.)

Resistor network RN1 is for port A bits, RN2 is for port B bits, and RN3 is for port C bits.



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