Quartus optimizing away my buffers

Hi Jake,

Thanks for your reply, it acctually does make more sense now that you've explained it like that, however im still concerned about one bit.

In your post you said "Quartus determined that these particular signals were always being driven from the specified locaiton and therefore simply turned them into wires."

My concern is that if it does indeed remove the internal muxes my design still won't work as intended.

The point of the buffers is to allow two sets of logic to drive the same output pins (which shall be connected to a memory chip), though obviously not at the same time. If you ask why I can't just disable the logic set while the other one is active, its because it will be writing to the Other memory chip.

In short, each logic set always tries to write to two sets of output pins, and the buffers are meant to block one or the other of these sets of signals.

I can see now though why Quartus may not 'understand' my circuit, since it has no concept of a high impedance state internally. I think I may have to redesign my switch with multiplexers explicitly.

Thanks!