On 3/11/2019 5:15 PM, Brent Hilpert via cctalk wrote: > On 2019-Mar-11, at 2:37 PM, allison via cctech wrote: >> On 03/11/2019 02:11 PM, Jay Jaeger via cctech wrote: >>> 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). > > . . . > >>> BUT - it also occurs to me someone may have already done something like >>> this? Any leads / ideas? > > . . . >> To do the data you need 8 bits but you can bit bang them out using two >> lines on a nano to >> a 74ls164. The rest you use transistors (open collector) to do high >> current (though 5V, >> 1K pullup is only 5ma) and I'd do that to make the IO more rugged and >> ESD proof. That >> covers the strobes and control lines. Just using two lines to get the 8 >> data lines via a 164 >> frees enogh pins for there to be surplus IO lines. > > . . . > > I've used an RPi for tasks like this in much the same way as Allison is > describing - > reduce the number of I/O pins needed on the modern microcontroller by > serialising > the legacy-device parallel data lines with a simple TTL shift register. > 2-4 pins (CLK,LATCH,DIN,DOUT, depending on app) from the microcontroller > can be translated to 8,16,32 or as many data lines as you need. > >
I had thought about an RPi as well. But the RPi is it is 3.3v, requiring additional hardware, which I'd like to avoid. A 5V Arduino (or a PIC, for that matter) should be able to drive the interface card's inputs on its own.
