Image Map Image Map
Page 1 of 10 12345 ... LastLast
Results 1 to 10 of 92

Thread: Saving ROM data from Tek 4052

  1. #1

    Default Saving ROM data from Tek 4052

    Been away from this forum for quite a while.

    I have a couple Tektronix 4052 systems and have one that works. I've received emails from other proud 4052 owners who are trying to fix their systems but theirs probably have bad ROMs. I don't think it's uncommon because both 4052s I have came to me in non-working condition. I got one up and running after I installed a whole set of NOS ROMs that a former Tek engineer gave me along with the 4052s.

    Now I'm worried about these ROMs going bad because if they give up the ghost then that's it for me. So I'm putting in some effort to preserve the ROM contents. There are two main types of ROM chips on the memory board that the computer uses for the BASIC interpreter, I think, and the chips are: 82S107 and MK36000. The 82S107 is not exactly a ROM, it's an oddball FPLA (Field Programmable Logic Array) that has tristate outputs! Going to be interesting to figure out how to preserve the contents of the FPLA and coming up with a modern replacement.

    The MK36000 seems like a fairly simple ROM chip. Does anyone have suggestions on EEPROM programmers or perhaps a design for a homebrew one that can read the contents off the MK36000? Or if someone has a spare EEPROM programmer...
    "One man's garbage is another man's treasure."

  2. #2
    Join Date
    Dec 2005
    Location
    Toronto ON Canada
    Posts
    6,784

    Default

    Not exactly trivial, but the 82S107 could probably be replaced by a modern (i.e. fast) (E)EPROM or PLD. Some clever folks did this to replace the 82S100 PLA in the Commodore C64 (and others IIRC); you might want to google and read about what they did. e.g.:
    http://www.nightfallcrew.com/?p=887
    http://mikenaberezny.com/hardware/pr...a-replacement/

    As you say, the MK36000 looks like it could be replaced with a 68764/66 or, with an adapter, a 2764 or equivalent.

    Most people recommend the Willem programmer.
    Last edited by MikeS; January 14th, 2010 at 09:13 AM.

  3. #3

    Default

    You could probably pump the ROM's data out with a BASIC program. I don't suppose you have the async comms board?

    Otherwise, didn't these things have GPIB/IEEE-488 ports? Of course, you'd also need something else that speaks IEEE-488 for that option...

  4. #4

    Default

    I've considered using the Arduino (can you tell I love the Arduino?) to read/test ROM and RAM. I did use it to test single-bit RAM chips in my SWTPC. However, you really need 8+log (base two) of the contents number of pins on the Arduino to test all of the addresses of an 8-bit chip without any external switches. With external switches though, you can use the Arduino to control a few of the address pins and the switches to control the rest. Then you can pipe that data from the ROM via USB/serial to your computer, which can put that into blocks of data. If I had an Arduino Mega, I would've already done this and possibly have made an EPROM programmer too!

    Kyle

  5. #5
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,332

    Default

    cosam,
    If there is a floppy on this computer, could it be possible to open a file for output and then set up a loop to do "print#1, peek(address +I)" and just peek the data to a sequential data file? Things to worry about would be to remember to set a "def seg = &HXXXX" to the correct portion of memory that will be read out.
    -Dave

  6. #6
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,332

    Default

    Quote Originally Posted by MikeS View Post
    Not exactly trivial, but the 82S107 could probably be replaced by a modern (i.e. fast) (E)EPROM or PLD.
    I see what you mean. Wow what a chip. I looked up the 82S107 as I have never heard of it. It is a Field Programmable ROM Patch. It can take 16 bit addresses and compare them to up to 48 stored addresses and if matched, output an 8 bit byte with a Flag to let the system know to disable the regular ROM for that read cycle.

    To emulate this one would not only need something like a 27C512 EPROM (64K X8 ) to store the 48 address traps but also a PAL to detect the 48 trap addresses and output a chip enable for the EPROM and the Flag for the system. And this assumes the PAL or PLD can handle 48 product terms.

  7. #7
    Join Date
    Dec 2005
    Location
    Toronto ON Canada
    Posts
    6,784

    Default

    Well, I don't think you could dump the 82S107 that way, but I wonder if you'd even have to; it's an unusual kind of chip, a ROM 'patch' that effectively lets you change up to 48 bytes in a ROM. If that is indeed how it's used in the 4052 then the 'effective' contents of the MK36000 would be all you'd need and you could just pull the 82S107. I suppose the 82S107 might even be empty if no patches were ever needed.

    In any case it shouldn't be too difficult to dump them both if you had to. The MK63000 looks standard and you could probably read it in something like a PC, but something to read the 'S107 might be hard to find and you'd probably have to breadboard something; then again, it's only 48 bytes

    Oops, looks like dave & I crossed in cyberspace

  8. #8
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,332

    Default

    I just realized that there is no reason to emulate the ROM patch chip 82S107. Just read out the complete ROM address space and save on floppy. The contents of the patch ROM will automatically be in the file. If anything goes wrong later with either chip, just replace both the ROM and patch ROM with an adapter for an EPROM with data from the saved file. Mike, am I understanding this correctly?

  9. #9

    Default

    Ah, I had no idea the 82S107 worked like that. I guess if you did the "PEEK loop" twice, once with the 82S107 present and once with it removed, you'd know all you needed to know. Writing to a file on a floppy sounds like a good way of doing it, assuming the floppy can be read on another machine without too much hassle.

    And yeah, it's only 48 bytes - I guess the trick is knowing which 48 bytes you're after ;-)

  10. #10
    Join Date
    Dec 2005
    Location
    Toronto ON Canada
    Posts
    6,784

    Default

    Quote Originally Posted by cosam View Post
    ...
    And yeah, it's only 48 bytes - I guess the trick is knowing which 48 bytes you're after
    Heh, heh, that's why I put the


    Yeah, sounds like we're all on the same page. I guess it hinges on whether you can in fact PEEK/dump that range either out a serial port or to a diskette that can be read elsewhere.

    FWIW, if you can't find (or your programmer can't handle) a 24-pin 8Kx8 EPROM (68764/66) then I think Jim Brain has some cheap 28>24 pin adapters (if you don't want to bother making one yourself).

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
  •