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PEB interface card replacement?

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I should probably do a 44-pin finger-board set layout, then the edge connectors in those things would be one piece, and much less finicky. Looks like I have another weekend project. . .

 

 

I was actually thinking something like the splitter except for 2 fundamental changes. Remove the straight through edge on the splitter (the one that continues to the right) and mount the the edge connector to the console at 90 degrees.

 

This would effectively turn the PEB connector on its side and feed it off the back of the TI instead of the side. May need a 3D printed foot for both the adaptor and the PEB connection. If you still wanted it to be a splitter, I suppose you could just add the passthrough back to its newly necessary position.

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I have one of those extension cables and have nothing but trouble with it, due to the two pieces of circuit board stuck into one end to make a male connector. The slightest jostle and it stops working, and is super fiddely to get working again. It wasn't cheap with shipping to Canada, either.

 

i have had good luck with both ones I have, but they never move too.

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I have one of those extension cables and have nothing but trouble with it, due to the two pieces of circuit board stuck into one end to make a male connector. The slightest jostle and it stops working, and is super fiddely to get working again. It wasn't cheap with shipping to Canada, either.

 

I have the same experience with both the extension and y adapters I purchased from that company with the brightly colored ribbon cable and the two pieces of circuit board

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I have the same experience with both the extension and y adapters I purchased from that company with the brightly colored ribbon cable and the two pieces of circuit board

 

i guess I was lucky.

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I found HD50 SCSI cables: 3ft for $34, 6ft for $38, 10ft for $42. Looking for matching circuit board mount ports. Could be worth designing an interface around?

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You probably want to go with the 3' or the 6', as 10' is too long for good signal propagation. This might actually work good though--as long as we can find something good to shield the cable with. . .

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You probably want to go with the 3' or the 6', as 10' is too long for good signal propagation. This might actually work good though--as long as we can find something good to shield the cable with. . .

 

The good ones are already shielded. As for signal propagation, if you shift the level of the signal rather you could get better propagation, right? Like EIA-232 signalling versus TTL for long distances (+/-12V) or some kind of differential.

 

Even so, I think 6ft should be good enough distance, anyway. How long is the firehose cable?

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In this case, I am looking for mostly user-proof rugged shielding, not the standard type of cable shielding. Maybe I could paint one with a layer of liquid electrical tape. . .that stuff is tough and flexible enough for this kind of application.

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I have been writing a specification over the past year for connecting the TI to the PEB using a standard off-the-shelf 40-pin IDE hard drive ribbon cable. My plan is to buy a 3-foot round IDE cable (the twisted pairs are separated and bound together in a rubber moulding) to make the appearance much more tidy, and use that to connect the two. I had to do some clever things to get everything to fit on the smaller IDE cable, but it should be doable. My specification is pretty much complete, just need to build a prototype and test it. Might be useful, as IDE cables are a dime a dozen and easy to find anywhere, eliminating the need for any special connectors or cables.

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Sounds like a great plan! Would the cable plug directly into the TI or will there be a need for an interface on that end?

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Sounds like a great plan! Would the cable plug directly into the TI or will there be a need for an interface on that end?

 

There would definitely need to be an interface on the TI's end to do the translation/multiplexing that allows 44 pins to be cut down to 40 (fewer than that, actually, since not all positions in an IDE cable are usable), but with modern PLD's, this logic won't take up very much space at all.

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I'm just curious which lines are being multiplexed? I was recently astonished to see Stuart's schematic for a breadboard TMS99110 that multiplexes the data and address lines, using a second signal to indicate when the processor is providing an address, or expecting to work with the data lines. I had not heard of or imagined an approach like that.

 

There only seems to be 38 valuable lines for the PEB on the sideport. ( removing +5v, -5v, SBE, and 3 extra duplicate grounds )

I've actually run the PEB off of the inner 40 pins on the sideport, and the only functional thing I lost is the audio pass thru. So that excluded the AUDIO, +5v, -5v, and SBE pins on the sideport.

 

[email protected]

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That being the case, then your 32k expansion is perfect for the idea of at 40-pin cable; just need the PEB side, yeah?

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I'm just curious which lines are being multiplexed? I was recently astonished to see Stuart's schematic for a breadboard TMS99110 that multiplexes the data and address lines, using a second signal to indicate when the processor is providing an address, or expecting to work with the data lines. I had not heard of or imagined an approach like that.

 

There only seems to be 38 valuable lines for the PEB on the sideport. ( removing +5v, -5v, SBE, and 3 extra duplicate grounds )

I've actually run the PEB off of the inner 40 pins on the sideport, and the only functional thing I lost is the audio pass thru. So that excluded the AUDIO, +5v, -5v, and SBE pins on the sideport.

 

[email protected]

 

I'll dig up my spec document for you all, but off the top of my head, I believe I multiplexed the *WE and *CRUCLK line. Consider that you're never writing to both memory and a CRU device at the same time. My TI-side interface would multiplex these two signals, and then the PEB-side would look at the other lines to figure out whether this was a memory write or a CRU write, and pulse the appropriate line. That's a very simplified explanation, but I've got more details to explain the rest once I post my spec doc.

 

That being the case, then your 32k expansion is perfect for the idea of at 40-pin cable; just need the PEB side, yeah?

 

If the goal is to remove the RAM from the PEB, then there would certainly be an opportunity to combine 32K of RAM onto my TI-side interface card. 32K static RAM chips are a few cents, and you can get them in tiny surface mount packages that take up almost no room. Would be worth designing it right in, along with a jumper to disable it in case you prefer to use a SAMS in the PEB.

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I think I would be just as happy to see a combination all of the efforts around here into a single, CorComp 9900 a-like project: a single side car with RS-232, 32k (or SAMS compatible,) PIO, DSDD controller with option for emulated devices via an SD/CF card through native floppy DSR or IDE interface.

 

I think I just described a nanoPEB with upgrades, but still. Maybe even an option for more expansion vis-a-vis the port on the 32k card. Hide the SS inside the box, add a video card, more sound, etc.

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I know some of us have even used a Flex Cable Interface cable extension to move the bulky cable out of the way and use the extension to neatly tuck under the console and to the expansion port.

 

Like this one.

 

Which can be found HERE

 

this is the exact one I use for this method.

 

I bought one and it works like a charm and is rock solid. The connector is one piece and not two as was stated by some, so maybe they improved it.

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I bought one and it works like a charm and is rock solid. The connector is one piece and not two as was stated by some, so maybe they improved it.

 

I examined mine closer and mine as well is only one piece.

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Well crud! Mine is a two piece, but it works perfectly.

I've purchased 4 at different times from the vendor, and which kind you get back is hit or miss. This seemed to be the case 25 years ago too. It's the 'foot' end anyway, which is the part you are trying to hide.

 

[email protected]

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I know some of us have even used a Flex Cable Interface cable extension to move the bulky cable out of the way and use the extension to neatly tuck under the console and to the expansion port.

 

Like this one.

 

Which can be found HERE

 

this is the exact one I use for this method.

 

 

I use this extension and it has greatly improved my desk space limitations. And it's fairly cheap, too, if I remember correctly. And I have had no connectivity problems with it at all since I purchased it about 9 months ago.

Edited by MillipedeMan

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I've purchased 4 at different times from the vendor, and which kind you get back is hit or miss. This seemed to be the case 25 years ago too. It's the 'foot' end anyway, which is the part you are trying to hide.

 

[email protected]

 

I shipped mine back as it didn't work, and they shipped me back one that didn't work either..

 

Greg

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Can you guys recommend a good source for a dual floppy drive cable for my system? Does the TI use the standard PC floppy cables?

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I've been wanting to throw my 2 cents in on this one.

I never produced it because cost for doing 2 PEBs was not doable on my budget - (even bulk buy of 25 boards + parts + 2.5' cable got it down to around $20, but still that's a lot of spares for something a few people might consider).

 

I'm dropping a blowup image of the 2.4" X 3.3" layout and an ExpressPCB .brd file here for anybody to use in hopes it might save someone time slogging through design/laying down traces/components OR just give someone another way of looking at the problem. :thumbsup:

 

Just a few notes:

1) TI-99/4A console end (foot) PCB + components to high-density 37-pin connector vs. HD-44 connector for cost (single ground line)

2) Mix of through hole and mostly 0805 SMT components (I'm sure size/footprint could be reduced further)

3) Obviously w/o silkscreen cost, "busy" nature of board could be reduced but I wanted pin out notes on available since there's not a nice 1:1 correlation to PEB end 44-pin connector (would have to be rewired as well with new HD round cable)

4) Other than PCB production cost, HD cables/connectors drive the price here

5) Adds a .5 amp 5V power source for accessories (via standard 2.1mm barrel connector powered from PEB)

 

 

post-48993-0-89616400-1494567487_thumb.jpg

TI-99HD2.zip

Edited by helocast
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