bad photo, but the traces are very clean in 8201. [image: Inline image 1] On Sat, May 2, 2015 at 4:39 PM, Stephen Adolph <[email protected]> wrote:
> 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 >
