CompuServe Messages

Dan, it looks like I misunderstood that chip's function. It doesn't exactly switch the denise between the two ports. It actually alternately looks at the directional signals and the quadrature signals (those are used on mice & trackballs only to give direction). So… I'd suggest powering up with the mouse installed. Look at pin 3 on the '157 while you roll the mouse forward or backward. Do the same on pin 2. You should see pulses. Then move to pin 4 and move the mouse forward again. That's the output. You should see pulses there. If not, look at pin 1. That's the clock line doing the switching of the '157. If that's missing, go back to a 74F74 at U8I and look at pin 9. That clock does stuff all over the system, so it's probably there. You could also try swapping out the denise chip, before getting too heavy with the scopin'. -Jim MOS via Autopilot & Amiga