I found the root cause for the 8300 hardware issue that Fred observed on both of his machines.
I'll send photos in the next three emails. REX uses /RD signal in 8201/8300 for timing. In 8201, the signal is very clean. See the photo 8201_std. In 8300, the signal has spurs. These spurs can sometimes cause REX to think it saw a clock pulse. Fred's and my 8300 both have identical looking signals. So I suspect all 8300 will have this noisy signal. See the photo 8300_std. The way to deal with this is to put a small capacitor on /RD. It acts like a sponge, soaking up the noise. See the photo 8300_1nF. When I modify REX8201 with this little capacitor, both Fred's and my 8300 seem to run REX software without problem. When I use a standard REX8201 in Fred's machine, it croaks during writes to flash, whereas my machine is fine and has never shown this problem. ..Steve
