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DEC RX02 Emulator - AK6DN

Hello, I find the project very interesting and have read your discussions
with interest. I developed the RL01/RL02 and MFM disk emulator and wanted
to merge both projects and additionally implement the AK6DN-RX02 emulator.
and maybe additional emulators for RK05 and RK07 as well.
My weak point is developing PCB boards and maybe you have a cheap hint who
can do something like that. I don't want to deny that I can't and don't want
to do it all alone anymore. However, my design is based on an FPGA, currently
a CYCLON V. Just wanted to ask how you see it. Reinhard
 
Well my first thought is why do a single board that is an RL01/RL02/MFM/RX02/RK05/RK07 emulator?
It makes much more sense to me to separate them out so someone who only wants an RX02 emulator is not burdened with the cost of all that other stuff.
Separate RL01/2, MFM, RX01/2, RK05, RK06/7 emulators would seem to be more user friendly to me.
PDP-8efm for example could only ever use RX01/2 and RK05, No sense using an FPGA based solution for those, way overkill.

Doing a native CycloneV board is going to be complicated as those are all dense BGA packages IIRC. Probably an add on board to some FPGA development board would make more sense.
 
PDP11GY said:
Hello, I find the project very interesting and have read your discussions
with interest. I developed the RL01/RL02 and MFM disk emulator and wanted
to merge both projects and additionally implement the AK6DN-RX02 emulator.
and maybe additional emulators for RK05 and RK07 as well.
My weak point is developing PCB boards and maybe you have a cheap hint who
can do something like that. I don't want to deny that I can't and don't want
to do it all alone anymore. However, my design is based on an FPGA, currently
a CYCLON V. Just wanted to ask how you see it. Reinhard
Click to expand...
Please tell us a bit more about your RL01/RL02 emulator (preferably in a new topic).
 
Thanks for link.
I now realize that the RL01/RL02 drives are only supported on a PDP-8/a by a RL8A (M8433) controller. :(
I would love to have a RK05 (emulated or real) for my PDP-8/e systems.
I have two sets of RK8E controller boards. :)
Did anyone ever create a non-commercial open-source RK05 emulator which connects to a RK8E (M7104/M7105/M7106) controller similar to Don's RX01/RX02 emulator?
Kyle's SerialDisk emulates a RK05 disk via a serial port, but I would like to use my controller boards.
Commercially available disk emulators which support RK05 are very expensive (Solid State Disk Ltd and Datex).
 
I have PDP11GY's RL01/02 project ... one more kit I need to put to work when I am retired.
What I wanted to say, is that his project allows a mix of _real_ *and* _simulated_ RL drives!
Very handy to copy real RL data cartridges to flash and then examine them on a PC in SimH.
No need to keep the real RL drives running for longer times, after all these beast are not the youngest anymore ...
 
Henk said:
I have PDP11GY's RL01/02 project ... one more kit I need to put to work when I am retired.
What I wanted to say, is that his project allows a mix of _real_ *and* _simulated_ RL drives!
Very handy to copy real RL data cartridges to flash and then examine them on a PC in SimH.
No need to keep the real RL drives running for longer times, after all these beast are not the youngest anymore ...
Click to expand...

I have not used this (I do not have any RL0x drives) but one issue I noticed is that the development is based on Quartus 16.1 which is NO LONGER offered for download.
Altera used to keep all the older downloads available, but Intel/Altera does not. The earliest version of Quartus now available for download is 17.0.
(excepting 13.0sp1/13.1 which is a special case to support legacy MAX cpld devices and Cyclone II).
I don't know how dependent the design is on any particulars of 16.1 with respect to using Altera IP software modules.
Usually it is relatively straightforward to upgrade the embedded IP, but not always as sometimes it changes more significantly.
Using the precompiled image provided should not be an issue I suspect but if recompile is wanted/needed it may require some source code changes.
 
First of all I would like to inform you that my emulators are full runable without downloading Quartus 16.1.
Just go to my homepage http://pdp11gy.com/rlstatusE.html and download the bootable ready for use
image file. You're right, Altera used to keep all the older downloads available. My projects are also
open source! Loading down Quartus 16.1. is only necessary for people who want to change or expand my
projects. So far I have not received an email or issue request via github to make the projects
compatible to the current Quartus version. Unfortunately, a lot has changed since Intel bought Altera,
especially for the free Quartus versions, like SD-RAM support. The infos on GitHub:
github.com

GitHub - pdp11gy/DEC-RL02-01-disk-emulator-reader-cloner-writer: rl02-01-disk-emulator-reader-cloner-(writer)

rl02-01-disk-emulator-reader-cloner-(writer). Contribute to pdp11gy/DEC-RL02-01-disk-emulator-reader-cloner-writer development by creating an account on GitHub.
github.com github.com
github.com

GitHub - pdp11gy/SoC-HPS-based-MFM-disk-emulator: MFM disk emulator ( ST506, ST412, ST225 ) based on DE10-Nano board

MFM disk emulator ( ST506, ST412, ST225 ) based on DE10-Nano board - GitHub - pdp11gy/SoC-HPS-based-MFM-disk-emulator: MFM disk emulator ( ST506, ST412, ST225 ) based on DE10-Nano board
github.com github.com
The most important information why I chose the FPGA solution based on the DE10-Nano board:
This board use the CYCLON V FGA which also contains a ARM Cortex-A9 CPU wich is binary compatible
for example to a Raspberry PI. Result: SIMH is also able to run on the DE10-Nano board. My projects
not only run in emulator mode but also in read/clone mode. This means, for example: An RL02 (or MFM/RD..)
disk can be read directly from the FPGA and the loaded software can be started immediately with SIMH.
And that's exactly what I would like to see for with the RX02 emulator from AK6DN.
Idea: connect a RX02 to the DE10-Nano FPGA bard via the interface from AK6DN, read the Floppies, start
SIMH with PDP8 simulator using the contents from the Floppies. There would still be plenty of room on
the DE10-Nano board, even an ARDUINO header connector.
But there are also problems: The DE10-Nano board is hardly available and has become relatively expensive.
The overkill hint from AK6DN : I also thought of a cheaper option:
Tang Nano 9K FPGA or Mercury 2 - Artix-7 FPGA DIP Board which I have already ordered for test purpose .
I also thought of a solution with a Raspberry PI/+PICO. The necessary clock frequencies could be generated
with an SI5351, perhaps replacing the DPR Ram with an I2 bus. but then everything becomes very extensive
and complicated.
Another exchange of experiences would be nice and maybe we should start a new thread.
 
PDP11GY said:
...
And that's exactly what I would like to see for with the RX02 emulator from AK6DN.
Idea: connect a RX02 to the DE10-Nano FPGA bard via the interface from AK6DN, read the Floppies, start
SIMH with PDP8 simulator using the contents from the Floppies. ...
Click to expand...
The RX02 emulator simulates the DRIVE side of the interface, not the CONTROLLER side.
It uses files that are direct images of an RX01/RX02 device, byte for byte copies, all tracks, all sectors.
Multiple files can reside on the emulator microSD card, it is just a normal FAT filesystem.
You can pop the microSD card into a PC and read/write the files to setup your images as you want.
Also the exact same files can be attached to virtual RX devices in SIMH.
So no real need to use my RX02 emulator attached physically to some system running SIMH.
Just use the files ...

Or am I misunderstanding something?
 
Last edited:
No misunderstanding. Was just a question. It's a bit of a shame. In any case, I have to do everything myself.
 
Theoretically one could make something like the RX02 emulator interface shield for a mega2560 that could operate as the controller side, instead of the drive side, of an RX.
Since the drive side is the master and the controller side is the slave of the interface, I think it would require at least a 16b shift register on the board in addition to the required open collector drivers and bus receivers.
So it would be a very similar style of shield, with a totally different control program on the Arduino, of course.
It could easily be set to copy floppy images off an RX01/02 media and store them to files on the microSD card FAT filesystem.

But of course any working PDP-8 or PDP-11 with a working RX drive can do the same thing already, imaging RX disks to files.
I suspect the demand for such a standalone disk copy device is much less than the demand for the RX emulator has been.
Wanting to replace an (unreliable) RX drive with a simple logical equivalent makes practical sense for everyday hobbyist use.
Even commercial use. I did sell one set of RX02 emulators to the last company that runs a Huey flight simulator.
It uses a dual 11/55 setup to run the simulator and it used to boot off a pair of RX02 drives, one for each 11/55.
Now the RX02's are stored for backup and the simulator boots off the RX02_emulators instead.
 
Just one last question: I took a closer look at the RX emulator.
As I understand it, this is not a real(time) emulator but a
very smart RX01/RX02 reader. I understand it like this:
The read data/images can only be simulated with SIMH but
can not copied to a real RX drive.
I expected the following(as with my RL01/RL02 and MFM emulator):
Assuming a RX controller, e.g. RX11, RX8, RX211, RX8, RXV11 and RXV21
is connected to the RX-emulator-board, than the RX-emulator-board behaves
like a real RX01/RX02 floppy and also a mixed operation of real drives and
simulated drives makes possible (like my RL simulator)
e.g. RX0=real , RX1= emulated.
Am I correct in my assumption?
I believe this feature can only be realized with an FPGA.
I will try as soon as I have enough time.
 
PDP11GY said:
Just one last question: I took a closer look at the RX emulator.
As I understand it, this is not a real(time) emulator but a
very smart RX01/RX02 reader. I understand it like this:
The read data/images can only be simulated with SIMH but
can not copied to a real RX drive.
I expected the following(as with my RL01/RL02 and MFM emulator):
Assuming a RX controller, e.g. RX11, RX8, RX211, RX8, RXV11 and RXV21
is connected to the RX-emulator-board, than the RX-emulator-board behaves
like a real RX01/RX02 floppy and also a mixed operation of real drives and
simulated drives makes possible (like my RL simulator)
e.g. RX0=real , RX1= emulated.
Am I correct in my assumption?
I believe this feature can only be realized with an FPGA.
I will try as soon as I have enough time.
Click to expand...

The RX02_emulator is a true, 100% functional replacement for a dual RX01 or dual RX02 physical floppy drive.
Your BOLDed sentence above is correct. Your final conclusion is not correct.

Connect the 40p flat cable from your DEC PDP-8efm RX8E/RX28 interface to the RX02_emulator and it 100% simulates the floppy drives.
Ditto for the DEC PDP-11 UNIBUS RX211 or RX11, or the DEC PDP-11 QBUS RXV21 or RXV11.
You can even run the original DEC PDP-11 Floppy Subsystem Diagnostics on the RX02_emulator and it passes 100%.

The RX02_emulator maintains the floppy images (which are SIMH compatible disk image files) on a microSD card formatted as a PC compatible FAT filesystem.
You can mount/dismount/remount images on the RX02_emulator microSD card via a text based menu subsystem thru the USB port.
It can also display real time status and debug printout of commands as they are executed.

Due to the architectural design of how the DEC RX drives are setup, it is not physically possible to have one RX drive be emulated and the other be 'real'.
The RL01/2 is different, the drives are daisy chained off the controller. The RX01/2 interface is a single point-to-point connection, dual-drive to controller.
Some users have added a second RX controller into their PDP-8/11 to have a mix of two real drives and two emulated drives (for imaging floppies, for example).

Also, because of the nature of the RX interface, the RX drive is the master and the RX controller in the system is the slave.
So no FPGA or high speed logic is required in the design, just translators and buffers.
The measly Arduino 2560 can actually emulate the RX faster than the real hardware.
 
Many thanks for your detailed explanation.
Then it makes no sense to start developing an RX emulator
for the DE10-Nano FPGA board. The only remaining question
is how do I get your RX emulator in Germany ( for a MINC system) ?
In any case, I wish you continued success.
 
PDP11GY said:
Many thanks for your detailed explanation.
Then it makes no sense to start developing an RX emulator
for the DE10-Nano FPGA board. The only remaining question
is how do I get your RX emulator in Germany ( for a MINC system) ?
In any case, I wish you continued success.
Click to expand...

I still have eight full parts kits left: PCB $10, microSD adapter $5, all discrete parts $15. US$30 total plus shipping. I have shipped kits all over the world, from Tasmania to Austria.

Full documentation and source here, including PCB gerbers if you so choose to go that route. Website: https://github.com/AK6DN/rx02_emulator
 
Playing with another design, this time an RX02_controller. (Will) emulate an RX211/RX11/etc or RX28/RX8E module connection to an RX02 drive (or even an RX02_emulator LOL).
Basic hardware design is all done and sent to pcb fab. Lots of software to do, as the Arduino control program is totally different that the existing RX02_emulator code.
Anyway, here is what it looks like in 3d rendering. Same 40p connector, same microSD card for local storage. Same kind of drivers (2n7000) and buffers (74ahtc14).
Interface logic coalesced into a CPLD (EPM7064S or ATF1504ASV). Local terminal interface via USB serial just like the RX02_emulator.

rx02_controller_3d.png
 
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