AR# 414: 2.1i: NGD2EDIF: WARNING:NgdHelpers:33 - NOTE: This design contains the undriven net "PRLD"
AR# 414
2.1i: NGD2EDIF: WARNING:NgdHelpers:33 - NOTE: This design contains the undriven net "PRLD"
Description
Keywords: 2.1i, ngdhelpers, 333, prld
Urgency: Standard
General Description: This warning appears during NGD2EDIF (timing netlist generator)
WARNING:NgdHelpers:333 - NOTE: This design contains the undriven net "PRLD" which you could drive during simulation to get valid results. writing EDIF file to 'time_sim.edn' ...
Solution
When a 9500* powers up, the registers can be preloaded with a value if the register is given an INIT=S property. If no init properties are assigned, all registers in the 9500* will power up with a 0 value. In the fitter report, this is listed as .PRLD - short for preload. Each register will have a .PRLD, and it will be set to GND unless you initialize it, in which case it will be set to VCC.
In order to simulate this preload on power-up, the PRLD signal needs to be toggled to set the registers in their proper power-up state. This warning is in regards to timing simulation only and has no effect on physical device operation.