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Thread: Netronics Explorer/85

  1. #11

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    I still have my old Explorer/85 and documentation if anyone needs more information. You are correct the the DB25 is for the serial port, but there were two different versions of the ROM monitor that supported either keypad or terminal. IIRC, there were also some jumpers that had to be installed differently.

    I'm currently building a functional clone of my old Explorer/85 using more modern components, like a single 32K EEPROM and 32K RAM. It's actually running Microsoft Basic/80 on a horrible rat's nest of wires on a solderless breadboard.

  2. #12
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    Thanks nib!

    I seem to recall reading in one of the online copies of the docs that the 'ikbd' chip was the ROM monitor? Is that correct? For some reason I can't find it now.

  3. #13
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    I agree there were two versions - one for the terminal using the serial port and one for a hex keypad that if I understand the documentation did not support the serial terminal. Interested in hearing more about your project - are you going to incorporate the s-100 as well? Is it a serial terminal version or the keypad version? Been looking for the contents of the keypad version - would like to convert one of mine.

    I have 3 EX-85s the one I am looking at has an 8355 with EXPL85 on it. My original has an 8755 that was a replacement from Netronics - a log time ago when it was my primary(Only) computer probably 1979 or 80.

    Jim
    Who let out the magic smoke!!!!!!!!!!!

  4. #14

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    The 'ikbd' doesn't sound familiar. The ROM monitor is contained in the 8355 chip. My monitor listing document is titled "Terminal Version" and there is no code in it to support the keyboard.

  5. #15

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    Jim - Definitely no S-100 or anything that ambitious. I was a poor high school kid when I build mine originally, so I'm just trying for something that will run Basic and the Monitor like the original. My new board is a simple 8085 with a single 32K RAM and a 32K EEPROM. The trickiest part was the power-on jump circuit that allows the RAM to be in the lower half of the address space. I'm trying to pull all of the project notes together to put the pieces on github. Along with the hardware, there's an Arduino-based programmer for the flash and a cross-assembler that is compatible with the format of the original Monitor source code.

    I've never run across the Monitor ROM for the keypad version. They were marketing this as a larger system and I suspect that they didn't sell a lot of the keypad variant.

  6. #16
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    That sounds like a pretty nice project is it working yet or do you still need files?

    Jim
    Who let out the magic smoke!!!!!!!!!!!

  7. #17

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    I got everything I needed by booting the old board and capturing monitor dumps to a terminal. The computer portion itself isn't very novel, but a few interesting tools came out of the project. I'll start a new thread when I get all the documentation together so I don't hijack this one any further!

  8. #18

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    falter,

    I just took another look at your photos and realize what you meant by ikbd. You are correct - that is the ROM monitor burned into an 8755. Mine is in the factory-programmed 8355 instead. I'll post a pic so we can compare boards. Yours has the connector for the keypad next to the 8755, so it looks like you do have the elusive keypad ROM. I'd be interested in seeing the differences between that one and the terminal version. I have the printed ROM source listing and have disassembled and reassembled mine to relocate a few things, so I'm familiar with the code.

    In this pic, one side of the serial port is going to and actual PC serial port. The other side had a blown transistor, so an FTTI chip (and an inverter) are connected directly to the TTL output. It put one side of the conversation in one terminal window and one half in another. Awkward, but it worked well enough to dump the contents of the ROMs.
    Exp85.jpg

  9. #19
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    May 2008
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    Do you have the actual manual for the monitor. I too spent time dissembling the ROM but I now have the manual. I too am interested in the keypad ROM. I did discover a lot came straight from the SDK-85 monitor so I suspect the Keypad ROM does too. Are those the Basic ROMs in your board curious as to what is on the labels?

    Link to Monitor listing and Basic user manual.

    https://dl.dropboxusercontent.com/u/...%20manuals.zip
    Who let out the magic smoke!!!!!!!!!!!

  10. #20

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    Those are the Basic ROMs. Two new photos are attached that show things a little clearer.

    Thanks for the link. I have those same manuals, same versions, although not scanned in. I should probably have the Basic manual under glass. It was probably stapled by Bill Gates himself.

    I originally tried to scan the Monitor source to OCR it, but the columns and the line wrapping were a mess. In the end, I scanned the last few pages of symbol table and OCRed them without too much trouble. Then used that and the binary as input the the most excellent dasmx and got a more-or-less exact copy of the source minus the comments. I've gone through and commented at least the breaks between the routines, so now I have a pretty good version of the Monitor source to work with.

    I've looked around for the SDK-85 monitor, but haven't found anything other than user manuals. At this point I suppose it doesn't matter much because I have good source to work with.
    IMG_2277.jpgIMG_2278.jpg
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