QPAD circuit board

The QPAD is my first-generation paddle card for developing Q-bus peripherals using a Burched B3-SPARTAN2+ developer's board (last year's version of the B5-SPARTAN2+ board). I built it in March 2002. It's a short Q-bus card with ten DS8641 transceiver chips on it, 180/390 ohm termination resistors for the various grant lines, and sockets for DIP termination resistor packs for all the other signals. I wanted to be able to use the same board for developing peripherals now, and possibly a bus adapter some day, so it needed to be able to terminate the CPU end of the bus if necessary.

The board is a half-height, double sided Q-bus board. I had it made at AP Circuits in Canada, they have excellent prices and fast turnaround for rectangular double-sided boards. Unfortunately they don't route board edges (they just shear them to a rectangle slightly outside the board edges you ask for) so I had to cut out the notches between the edge connectors by hand, to fit the Q-bus sockets.

I have the board mounted on an extender card out of a BA11-VA desktop 4x2 Q-bus chassis (with an LSI-11/73 CPU, aftermarket 2 MB block mode memory, and DLV11J quad SLU board in the other three slots), and it's connected to the Burched developer's board with five 20-pin ribbon cables.

The developer's board is programmed using Xilinx's free Webpack software. I wrote VHDL code (which was frustrating, this was my first VHDL project and I find the popular textbooks are very light on practical information) to handle CSR accesses, generate interrupts (including priority arbitration), and perform DMA (including block mode if available). However, since I found out too late that the 80186 and Am186 have been discontinued in all their forms, I realize now that there's no point in continuing development with a PC host, since I will have to use something other than an 80x86 CPU on the actual peripheral.

OK I don't know why I thought that, AMD's out of the '186 business but the Intel 80186 is alive and well in several forms, and the 386EX looks even better. So I'm working up a design for a prototype CPU card with one of those on it.

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