There are packaging options which might be utilized to help you in "scoping" out your circuit. One of many complaints I have about FPGA's is that they have far too many pins to suit me. Well, since there are lots of pins, you can obtain a socketable adapter for the package and then work your way through the design, changing the "bond-out" by routing the signals you want to compare to I/O blocks associated with otherwise unused pins. That way you might be able to help yourself figure out strange timing effects between internal and external signals, perhaps even allowing you to see the inner workings at least to some extent. The handiest package I've run into for these is the PLCC84, for which you can obtain a socket compatible with a wire-wrap adapter. That would allow you to do what I described above without interfering with the 40-odd signals you might want to inject into your existing application. This same thing might be achievable with a larger package, but I have some doubts about making the transition from the FPGA package to a wire-wrap socket. You might have to make an adapter PCB or buy one from Samtech or Emulation Technology. Those get expensive. Dick -----Original Message----- From: allisonp(a)world.std.com <allisonp(a)world.std.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Monday, August 30, 1999 12:03 PM Subject: Re: FPGAs and PDP-11's