I have several PDP-11's in my collection (among other things), and not enough PC05 tape readers (or enough room) to go around. But most if not all of my machines have M7810 PC11 interfaces, and I have one I could move from machine to machine as needed. Moving a PC05 around would be a lot more work, and not every rack has room. ;)
So, I took a look at what it might take to interface with an M7810 (or, down the road, a PDP-8/L or PDP-12. It looks like the emulator would have to accept as input just 3 lines (Initialize L, IOP2(1)/Select, IOP4(1)/Read) [It would not need the redundant Initialize H, IOP1(1), Qualify or Skip], and would have to drive 11 lines into the pullups on the M7810 (8 Data lines, IO Bus INT L/Reader Done L, Outtape/Error and RDR RUN L/RDR Busy L). So, a total of 14 interface lines. (The 8 or 12 would take a few more lines). The pullups average about 470 ohms (1 is 1K, 1 is 220, the rest are 470), so at 5V the output has to sink a bit over 10ma, and all total 120ma. An Arduino Uno with an Ethernet shield would have 20 minus 5 lines available, in theory, but if one wants serial I/O as well for debugging, that sucks up 2 more lines - so only 13 available. And sinking 120ma would be a bit much though I could likely sprinkle inputs among the outputs to make it work so as to stay within the recommended sink limits, and at least initially have it never run out of tape, and tie Error down. http://playground.arduino.cc/Main/ArduinoPinCurrentLimitations So, I am thinking about an Arduino Mega, as it has more output groupings to sprinkle the sink current around, and 5V interface capability, and more pins to eventually support my PDP-8/L and PDP-12. (I could do it with a PIC - did that for a Documation card reader to PC interface, but I am really tired of fighting Microchip's IDE.) BUT - it also occurs to me someone may have already done something like this? Any leads / ideas? JRJ
