Shift838 Posted January 21, 2017 Share Posted January 21, 2017 I'm thinking of making my own cartridge extension cable for the 4A and I am wondering if there is a length I should not go past to ensure signal strength. Anyone know or have a recommendation ? 1 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted January 21, 2017 Share Posted January 21, 2017 Note: GROMs are relatively weak line drivers, per the TI Specifications, so you really don't want to make the cable too long. I know that a cable about a foot long is safe, I haven't tried anything longer than that. 1 Quote Link to comment Share on other sites More sharing options...
+helocast Posted January 21, 2017 Share Posted January 21, 2017 Given: http://www.farnell.com/datasheets/577969.pdf it appears ribbon cable introduces around an average of 45pF/39.4" loading (depending on type/brand/shielding chosen). Given: Console and peripheral Expansion System Technical Data, signal driver maximum pF before affecting timing/signal strength (page 12-14 attached jpegs) are maximum pF per respective signal pin. Given: Real-world PEB cable length of ~ 57" BEFORE hitting first 74LS244 (octal driver/transceiver) "buffer" it seems to be P.F.M. ... but it works. Note: Exceptions are the D0-D7 lines which get double buffered again at about five inches and then again at 57" compliments of two 74LS245 chips. Plus TI's specification states you need another set of 74LS244/74LS245 on each peripheral card as additional insurance? While that mouthful sounds like I know what I'm talking about, I'm not an engineer and I barely understand the constraints/implications ;-] At http://iec.net/?s=TI99&post_type=product their http://iec.net/product/ti994a-side-port-extension-16-inches/ product seems to get away with 16", but I have no experience with them (yet) as to what kind of signal degradation actually occurs by the end of that 16". For the popular mod of moving the speech circuit inside, the poor little speech SBE signal @ 25pF maximum driving load (if using that line) seems the limiting length factor is about 21.9"? Critiques welcome! 1 Quote Link to comment Share on other sites More sharing options...
+helocast Posted January 21, 2017 Share Posted January 21, 2017 After researching I/O vs. GROM port (reading is fundamental) http://iec.net/product/ti994a-cartridge-port-extension-8-inches/ but I haven't tried them =] 1 Quote Link to comment Share on other sites More sharing options...
Shift838 Posted January 23, 2017 Author Share Posted January 23, 2017 Another question on the cartridge port.... I know will plug in to a cartridge upside down. My question is are the pins on the cartridge port itself just wired straight through on the cartridge port circuit board? I ask because my plan to convert a 5.25 drive bay into a cartridge port will work, but it looks like it will work better if I mount the cartridge port upside down. If it is wired straight through on the circuit board then I should be able to mount it upside down and as long as the extension cable is backwards I can still plug in the cartridge port right side up and it will work. Not sure, so I need to TI Gurus to answer for me. thanks, Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted January 24, 2017 Share Posted January 24, 2017 The cartridge port on the motherboard without the right angle grom port adapter has the top and bottom layers swapped. So a top layer connection on the cartridge is a front connection on the motherboard. ElectricLab and I observed this a couple weeks ago just looking at the right angle adapter. The implications are you can't just rotate the cartridge. -M@ 1 Quote Link to comment Share on other sites More sharing options...
Sinphaltimus Posted February 4, 2017 Share Posted February 4, 2017 The cartridge port on the motherboard without the right angle grom port adapter has the top and bottom layers swapped. So a top layer connection on the cartridge is a front connection on the motherboard. ElectricLab and I observed this a couple weeks ago just looking at the right angle adapter. The implications are you can't just rotate the cartridge. -M@ JM@T - Can you elaborate for me? I just recalled this comment from you as I'm doing the schematic for my cart expansion. The pin out diagrams I see have pin 1 in the lower left corner and pin 2 above it. Are you saying that via the 90 degree adaptor, the pin1 is top left and pin 2 bottom left and that this is the correct orientation for a cartridge insertion? So all my GROM ports pin1 should be upper left and represent the top edge of the connector on the cart? Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted February 4, 2017 Share Posted February 4, 2017 Top row are the even numbered pins, but they are counted from the left side of the connector. . .so the row of pins closest to the console should be the even numbers to make it match with the cartridge port. 1 Quote Link to comment Share on other sites More sharing options...
RXB Posted February 5, 2017 Share Posted February 5, 2017 I had a connector that had a few more pins on one side and used it to plug into the Cart port and just put our L adapter on other end with cart or GRAMulator. I was long enough to put the cart on the power side behind the TI99/4A maybe a foot or longer ribbon cable with aluminum foil cover with plastic. I found it in a bin of Main Frame parts years ago. It was picking about moving the cable to to much. Quote Link to comment Share on other sites More sharing options...
Sinphaltimus Posted February 5, 2017 Share Posted February 5, 2017 Top row are the even numbered pins, but they are counted from the left side of the connector. . .so the row of pins closest to the console should be the even numbers to make it match with the cartridge port. So like this? Quote Link to comment Share on other sites More sharing options...
fabrice montupet Posted September 21, 2017 Share Posted September 21, 2017 (edited) Some tests showed me that GROM only cartridges accept easier a long port extension cable. When ROM chips are present, problems begin. The ROM time access is also very important: I have tested two TI Extended basic cartriges, one was working, the other not. When I opened them, I noticed that the first one have faster ROM. Edited September 22, 2017 by fabrice montupet 3 Quote Link to comment Share on other sites More sharing options...
jrhodes Posted December 17, 2019 Share Posted December 17, 2019 On 1/21/2017 at 11:44 AM, helocast said: After researching I/O vs. GROM port (reading is fundamental) http://iec.net/product/ti994a-cartridge-port-extension-8-inches/ but I haven't tried them =] Does that cable plug into the right angle grom port adapter (where the cart normally plugs in) or does it go directly onto the TI motherboard? Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted December 17, 2019 Share Posted December 17, 2019 It plugs into the same port as the cartridge--at the cartridge port, not at the motherboard. 1 Quote Link to comment Share on other sites More sharing options...
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