Post by Tom HunterSorry for the resend. There appears to be no way to directly reply to
an author of a message. Rob Doyle - is there any more information
about using your PDP8 implementation on a DE0-Nano?
It builds and programs fine into the DE0-Nano, but without anything
connected to the boards headers it won't do much.
Have you got any schematics or design for a plug-on board for what
needs to go onto the DE0-Nano headers to make the PDP-8 functional?
It is a bit confusing because you did bring out all the switches but
not the data and address LEDs. Also there is code there to show the
data via a 4 digit 7 segment display, but that too does not connect
to the headers. The 7 of the 8 LEDs which came out are not used but
seemed to be some form of debug LEDs which have been commented out.
Is this still work in progress or am I looking at the wrong
Subversion branch?
The website is: https://opencores.org/projects/pdp8
I am looking at the code in Subversion under trunk.
Thanks and best regards Tom Hunter
[snip]
Short answer - someone contributed the DE0-Nano top-level design. I know
that I built it and that it built without errors - just to make sure it
was complete. I have a DE0-Nano but used it for a PDP2011.
You will need an external 3.3V to RS-232 adapter of some sort and if you
want an SD Card socket if you want to implement an RK05 disk drive. It
has been a long time, but I believe the author used a Digilent SD
Card PMOD and a UART/USB PMOD.
If you look at the directory structure, there is fairly generic PDP8
implementation underneath everything which has standardized interfaces
for all of the external interfaces - RS232, Front Panel, RK05,
configuration, etc.
At the top level, you can configure the PDP8 and implement or 'stub
off' the interfaces as you see fit. So, yes, several of the FPGA boards
have 7 segment LED displays. All the switches and LEDS (address and
data bits) are routed to the 'top level' entity. Depending on what top
level entity you're looking at, they may be 'tied off'.
I have a whole design of a front panel board that was intended to be
compatible with my SBC6120 PDP8 unit. It has all the switches, LEDS, an
SD Card, a socket for DE0-nano, 4x RS232 ports, a FT4232 quad USB/UART,
VT52 terminal with VGA video and PS/2 keyboard interfaces, and a WIFLY
module. It's designed in KICAD and is mostly all done. I just never had
time to finish it. By now, it probably has some obsolete parts - and it
would take a little to clean the design up. The FPGA interfaces to bhe
board would need to be implemented - but this is relatively simple.
I'd share that design if someone had the energy to finish it and let me
order one of the boards.
Rob Doyle
doyle (at) cox (dot) net