I’ve written about fillwords a lot (see here, here, and here) but I didn’t show you much about the different symptoms an incorrect fillword setting may incur.
As you’ve seen fillwords are a very nifty way of maintaining bit and word-sync on a serial transmission link when no actual frames are sent. Furthermore they also are replaceable with other primitive signals (Like R_RDY, VC_RDY etc) to utilize a very simple instruction method between two ports without interfering with actual frames. That means that fillwords are ALWAYS squeezed in between frames.
