Honored Contributor
Honored ContributorHi Vadim,
Global pins should be used for global signals such as clock and reset. Have you tried performing a timing analysis using Quartus? The MAX3000 devices are simple devices, so they are unlikely to be flexible with which pins can be used without Quartus giving warnings. For example, create a design containing multiple instances of counters with clock and reset inputs, and perhaps route all carry-outs to pins. Assign the clock and reset to global pins, synthesize the design, and look at the timing. Then change the clock or reset to a non-global pin and see how the timing changes. To get a better feeling for how the timing changes, try and fill the device with counters, and try changing the counter widths. To answer your specific questions; clock and reset should use global input pins (these are usually listed in the pin files for the devices and in the Quartus pin planner GUI). Your tri-state outputs can be controlled however you see fit, eg., by logic within the MAX3000 or an external control signal. Its unlikely that OE needs to use a global input, but there is no harm in using one either. You do not need to use OE at all if the signal from the MAX3000 is an output-only, i.e., only routes to the inputs of external devices. Cheers, Dave
