Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

Frequency doubler with xor and delay

hello, I need to double an input frequency (input frequency range 1KHz-100KHz) using an EPM1270 MAX II device. I know that it is possible using an XOR gate with a lot of delay on one of the inputs...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

Firsly look at the post snythesis netlist (technology map viewer). Most likely the inverters have been discarded during synthesis. Read about the "synthesis keep" attributes that have to be applied. There are several previous forum threads about generating logic cell delay.

Your expectations about the delay are probably wrong. I would calculate about 0.25 ns per LE with MAX II or Cyclone series.