Setting Pulldown on the PMOD Pins (Nexys A7)
'PULLDOWN' attribute/property is deprecated. You can do it using 'PULLTYPE' attribute instead in Vivado. Either apply this attribute in your RTL code, or in the XDC constraint file. Writing in the XDC file makes the RTL more portable. You can write a separate line in XDC for that port:

set_property PULLTYPE {PULLDOWN} [get_ports &lt;port_name&gt;]

Refer Page 319 of this Vivado Document for more details.