Announcement

Collapse

Forum etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


"PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

EPROM Emulator

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • pbirkel@gmail.com
    replied
    Originally posted by MicroCoreLabs View Post
    Are you going to start a similar project?
    Not at the moment, anyway. Thank you for pointing out the location of the BOM!

    Leave a comment:


  • pbirkel@gmail.com
    replied
    Originally posted by Al Kossow View Post
    it appears to be an obsolete TI part, 74LX245B originally made by Fairchild
    Ah. I can't tell my "8" from a "B" :-<. THX1

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by pbirkel@gmail.com View Post
    Question about the 74LS245 in the circuit, what is the 245 type you used? HC?



    Where is the BOM located, please? I don't see it in GitHub. The schematic states 74LS245 but specifies 3.3VDC. Your web pages states "SMT buffer". The visible markings on the eBay listing are nondescript (or at least indecipherable by me); LX2458 doesn't seem to correspond to any TI part.

    My best guess is that these are actually TXB0108 but its pin-interface doesn't agree with your schematic.

    Thank you for clarifying this point.

    paul

    Hi,

    The BOM is on GitHub here: PCB/PCB_FIILES/BOM.txt

    The parts are the SN74LVT245BDBR which are 3.3V parts that are 5V tolerant. This part symbol is not in KiCAD, so I probably used whatever x245 parts that was available.

    Are you going to start a similar project?

    Thx
    -Ted

    Leave a comment:


  • Al Kossow
    replied
    it appears to be an obsolete TI part, 74LX245B originally made by Fairchild

    Leave a comment:


  • pbirkel@gmail.com
    replied
    Question about the 74LS245 in the circuit, what is the 245 type you used? HC?

    Originally posted by hanso View Post
    Ok, the BOM is uptodate!
    Where is the BOM located, please? I don't see it in GitHub. The schematic states 74LS245 but specifies 3.3VDC. Your web pages states "SMT buffer". The visible markings on the eBay listing are nondescript (or at least indecipherable by me); LX2458 doesn't seem to correspond to any TI part.

    My best guess is that these are actually TXB0108 but its pin-interface doesn't agree with your schematic.

    Thank you for clarifying this point.

    paul

    Leave a comment:


  • MicroCoreLabs
    replied
    I posted a few copies of the EPROM Emulator on eBay: https://www.ebay.com/itm/154425061318

    And of course the project is open-sourced, so you can build your own: https://github.com/MicroCoreLabs/Pro...EPROM_Emulator

    Leave a comment:


  • MicroCoreLabs
    replied
    If using the Teensy 4.1 it could probably also implement both the cartridge emulation as well as this functionality: https://www.raphnet-tech.com/product...rtJR/index.php

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by psergiu View Post
    Could this be used in a PCjr cartridge ?
    Can it hold multiple 64k images and switch between them (rotary selector connected to any spare GPIO pins) (most likely will require a Teensy 4.1 as your design uses ALL 24 Teensy 4.0 pins)
    32 in 1 multi-game Cart for PCjr
    And with Teensy 4.1 it could even load the ROM images from the microSD.
    See: https://www.raphnet.net/electronique...e/index_en.php
    Yup, totally could!

    Switching ROMs could possibly be done in other ways so a Teensy 4.1 would not be necessary... Maybe use a menu accessed through UART communication with the Teensy 4.0... Or perhaps have the Teensy snoopy for write accesses to a particular address or sequence of addresses to switch the ROM image.

    But yes, if a Teensy 4.1 was used we could have a physical switch and all ROM images could be stored on he microSD or in the 1MB of Teensy ROM. No software or special BIOS would be needed to run on the PCjr to access, load, or switch the images...

    Leave a comment:


  • psergiu
    replied
    Could this be used in a PCjr cartridge ?
    Can it hold multiple 64k images and switch between them (rotary selector connected to any spare GPIO pins) (most likely will require a Teensy 4.1 as your design uses ALL 24 Teensy 4.0 pins)
    32 in 1 multi-game Cart for PCjr
    And with Teensy 4.1 it could even load the ROM images from the microSD.
    See: https://www.raphnet.net/electronique...e/index_en.php

    Leave a comment:


  • atg
    replied
    This is great. I will follow this thread.

    I am light on cash right now, and my solution to not having the diagnostic rom for the 5150 is to use an FPGA to emulate it. We shall see how that goes...

    Leave a comment:


  • hanso
    replied
    Originally posted by hanso View Post
    Interesting! Really like the small footprint. Question about the 74LS245 in the circuit, what is the 245 type you used? HC?
    Ok, the BOM is uptodate!

    Leave a comment:


  • Ruud
    replied
    Originally posted by MicroCoreLabs View Post
    Funny... You were exactly the person I was thinking of as someone who could use this!

    Did you use a similar emulator for your diagnostic rom work? Or programmed EPROMs for each iteration?
    I first placed a 32-pin socket plus converter to 28 pins in the original socket and then used 29F010 EEPROMs to test things. Not the fastest way but much much faster than EPROMs.

    In the mean time I created my own emulator. This page isn't up to date, it doesn't mention yet that I want to use an Arduino instead of a LPT port. But you design is much neater than mine, just the very small size is a feast to the eyes!

    Leave a comment:


  • hanso
    replied
    Interesting! Really like the small footprint. Question about the 74LS245 in the circuit, what is the 245 type you used? HC?

    Leave a comment:


  • MicroCoreLabs
    replied
    The C code, schematics, and PCB files are now on GitHub: https://github.com/MicroCoreLabs/Pro...EPROM_Emulator

    In theory, this board could also be used to trigger on a sequence of addresses and then print something out of the UART. It could also report the progress the BIOS makes during self-test; similar to a POST board. In addition, if the history of addresses was also stored in a buffer, then if BIOS detected an error we could print the addresses that led to it...

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by Ruud View Post
    What struck me: small! Nicely done and I'm looking forward to the Github link. Please keep us informed!
    Funny... You were exactly the person I was thinking of as someone who could use this!

    Did you use a similar emulator for your diagnostic rom work? Or programmed EPROMs for each iteration?

    Leave a comment:

Working...
X