AR# 1051: XNFPREP: Error 3526: Illegally inverted pin with XBLOX SYNC_RAM symbol
XNFPREP: Error 3526: Illegally inverted pin with XBLOX SYNC_RAM symbol
Keywords: xnfprep, error 3526, xblox, RAM
During compilation of a XC4000E design containing an XBLOX SYNC_RAM component, XNFPrep may give the following error:
XNFPREP: ERROR 3526: The pin 'D' on the symbol <symbol name> (type = RAMS, output signal = [signal name]) is illegally inverted. This pin in non-invertible.
This error is occurs while placing either an INVBUS symbol or INV symbol on the WR_CLK pin to clock the synchronous RAM on the falling edge. XBLOX pushes the inversion onto the device pin instead of leaving the inverter separate as it should.
Place an X (explicit) property on the net between the INV/INVBUS and the SYNC_RAM. This will prevent the inverter from being absorbed into the D pin of the synchronous RAM.