The asynchronous feedback loop on the err signal causes X to get stuck
on the sum signal when simulating. This change adds a check for
simulation only to force X to 0 so that unknown inputs get resolved
once the inputs are known.
Also added default values to the ports out and strobe_out, since having
them uninitialized and without reset was causing simulation issues in
other modules. The FPGA will initialize them to 0, so this change makes
the code equivalent to real hardware behavior.
Original-commit: b9f7af5807f73a5ac2612ea42ac2b65c26a3bff2
Wade Fife
776860727e