Image Map Image Map
Page 18 of 18 FirstFirst ... 81415161718
Results 171 to 176 of 176

Thread: PDP SBC - J11 Hack

  1. #171
    Join Date
    Apr 2017
    Location
    Switzerland
    Posts
    248

    Default

    Finally found some time to continue with my project. The next step was to check DMA functionality. To be able to test the CPLD Design I added a simple DMA "device".

    IMG_1946.jpg

    As you can see I just added a AVR (Atmega1284P) via a breadboard to the Q-BUS64. This "device" can actually only perform DMA. It is not a real device, it does not have device registers. To perform a DMA you need to connect to the program running on the AVR via a serial line and enter commands to transfer from/to the PDP-11 Memory to/from the AVR RAM, e.g.

    Code:
    1/1000<3000.30ffw
    writes the contents of AVR Memory 0x3000 to 0x30ff (users of a Apple IIgs might find the command syntax very familiar) to the PDP-11 Address 0x11000 (which translates to 0210000 octal) and there is a similar command to read from the PDP-11 RAM, i.e.

    Code:
    3100<1/1000.10ffr
    would read back the previously written memory range to the AVR RAM address 0x3100. There are more Apple II like commands that allow to inspect, change and verify AVR RAM content so with

    Code:
    3000<3100.31ffv
    I can verify that the values written and read back via DMA are identical. For those interested I have added the latest CPLD Design file.

    PDP11EURO-V1-0.txt

    And of course the most important news is that DMA is working as expected. The AVR program is not optimized at all, so with the current version DMA throughput is approx 300kbytes/sec, the DMA word write cycle itself takes about 2.5microseconds. Also for the moment I only support word transfers and no byte transfers. But that is not important as diskcontrollers do not make use of DMA byte transfers.

    With this the CPU board is mostly finished and ready for the next step, a real disk controller. Here I would really appreciate some help.

    Peter

  2. #172
    Join Date
    Jul 2016
    Location
    Sunnyvale CA USA
    Posts
    9

  3. #173
    Join Date
    Apr 2017
    Location
    Switzerland
    Posts
    248

    Default

    Hi,

    Brent has put his homepage online again at http://madrona.ca/e/pdp11hack/index.html and my project has reached a full working status https://www.5volts.ch/pages/pdp11hack/. Currently I'm in the process of clean-up of all the code and working on a better documentation.

    Peter

  4. #174
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,155

    Default

    Nice job Peter.

    I especially like the thorough commenting in the WinCUPL source files - an excellent example for everyone reading them!

    Question, is anyone going to make kits of parts - or even built boards - available for this project? I wouldn't mind getting my hands on a set of pre-built cards...

    Dave

  5. #175
    Join Date
    Jun 2014
    Location
    Salt Lake City, Utah
    Posts
    517
    Blog Entries
    1

    Default

    ditto that on, will take a board set.

    I got distracted on other projects and pulled my breadboarded pdp11 hack apart. Glad to see you stuch with it Peter.

    Len

    Quote Originally Posted by daver2 View Post
    Nice job Peter.

    I especially like the thorough commenting in the WinCUPL source files - an excellent example for everyone reading them!

    Question, is anyone going to make kits of parts - or even built boards - available for this project? I wouldn't mind getting my hands on a set of pre-built cards...

    Dave
    Spread the joy of Vintage Addiction

    -->www.chronworks.com/<--->www.i8008.net/<--

  6. #176
    Join Date
    Apr 2017
    Location
    Switzerland
    Posts
    248

    Default

    I can fork some PCBs (Bus, CPU+Memory, Multifunction, RLV12) and give some advices, but the rest is up to you.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •