Thinking about PDP11 PC05 Emulation

[Jay Jaeger]

Hi, Henk.

Cool - so sort of the complement of what I am considering doing - your
interface allows connection of a real device to a simulated hardware
processor.

Your thorough documentation will be helpful in confirming the signals I
plan to use.

JRJ

On 3/11/2019 1:39 PM, Henk Gooijen wrote:
> Hi Jay,
> 
> Have a look at www.pdp-11.nl/peripherals/tape/pc05-simh-pc.html
> <http://www.pdp-11.nl/peripherals/tape/pc05-simh-pc.html>
> 
> If you are interested I can tell you more …
> 
>  
> 
> I can read and punch tape. PC05 + interface (PIC 18F4550) connects using
> RX/TX to USB to PC.
> 
> Reading one character at a time works fine (speed some 20 char/sec,
> so-called start-stop mode).
> 
> Reading in “streaming mode” is probably some 300 char/sec, but I get
> unexplained “out-of-paper” state sometimes, and reading stops (of course).
> 
>  
> 
> To read from the PC05 reader you need IOP2, IOP4, and INT*. Maybe BUSY*
> is needed, not sure about that.
> 
> INITIALIZE* is good to have as well. A few other signals (for example
> IOP1) needs to be connected to an appropriate level. And 8 data inputs,
> which need a pull-up resistor. Note that the data from the reader is
> inverted.
> 
>  
> 
> To punch you only need IOP4 (IIRC) and of course 8 data outputs.
> 
> As you know, reader and punch are two completely isolated devices.
> 
>  
> 
> Greetz,
> 
> Henk
> 
>  
> 
>  
> 
> ------------------------------------------------------------------------
> *Van:* cctech <cctech-bounces at classiccmp.org> namens Jay Jaeger via
> cctech <cctech at classiccmp.org>
> *Verzonden:* Monday, March 11, 2019 7:11:46 PM
> *Aan:* General Discussion: On-Topic Posts
> *Onderwerp:* Thinking about PDP11 PC05 Emulation
>  
> 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