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TI-74 and cassette capabilities


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#51 acadiel OFFLINE  

acadiel

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Posted Sat Nov 24, 2018 3:07 PM

There is a Hexbus IC on the board. I was assuming pass through, but maybe it's for something else. I'll have to pull it apart again.

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#52 Opry99er OFFLINE  

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Posted Sun Nov 25, 2018 8:55 AM

Will this work with the CC40 as well?

#53 arcadeshopper OFFLINE  

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Posted Sun Nov 25, 2018 11:37 AM

Will this work with the CC40 as well?

If it's hexbus it's the same just a different pinout

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#54 Jeff_Birt OFFLINE  

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Posted Sun Nov 25, 2018 4:02 PM

There is a Hexbus IC on the board. I was assuming pass through, but maybe it's for something else. I'll have to pull it apart again.

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The big IC is a 'line driver' which just means it has higher current outputs for driving a heavier load. I suspect they used it as a buffer and/or inverter for the 3 I/O lines used.

 

Will this work with the CC40 as well?

Yes, the TI-95 and TI-74 added two pins to make a 10 pin connector. The extra two pins being a 6VDC input to the calculator (which my interface supplies so when you are using the cassette interface you are not running on batteries) and a 6V output. The cable between the adapter and the CC40 would be different. I recently picked up a CC40 and have not used it yet. I'll look at making a cable for it as well. In the design files linked in the video there is a PDF of the schematic (in case you don't use Eagle)  which shows the pin outs of the TI-95 connector and adapter connector.

​If there is interest I'll see about getting a small number of PCBs made by OSHpark or someplace so if you want top make on you would just have to buy the components. If there is a really enough interest I might think about putting together 10-20 kits of the PCBs, components and 3d printed case so you can solder it together.



#55 HOME AUTOMATION OFFLINE  

HOME AUTOMATION

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Posted Sun Nov 25, 2018 5:50 PM

Doh! Forgot the link 

 

 

Hi,

 

While flipping though your video... I was intrigued by your mentioning the TI-74 cassette interface's ability to sense voltage or current initiated by pressing a button on the player/recorder, causing the remote line to become active. I did not catch what the response is by the TI-74.

I'm curious because I have a particular TI-99/4a which exhibits an interesting response to a particular unused input port on the 9901 being held LOW(Port 10, Pin 29,SBO\SBZ 26), normally held high by a pull-up resistor. While held LOW the system hangs indefinitely and waits for P10 to go high... at any of the times that a prompt for cassette operation would normally appear. It has been speculated that this was in provision for a more automatic type of data drive never implemented by TI. I'm now wondering if this instead was something concieved to work with regular cassette recorders.



#56 Jeff_Birt OFFLINE  

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Posted Sun Nov 25, 2018 6:33 PM

The 'sense' line is an output of the Commodore C2N datasette. It was made use of by the Commodore 64/VIC-20 originally. The TI-95 does not have any provision for this as far as I am aware. Since the CI-7 tape interface was designed for use with a normal cassette deck which would not have had a key sense output.

 

It is curious though that TI-99/4a has an input pin that acts as though it was made for that purpose given that they had a similar three wire analog tape lead, though they did use a DB9 connector on the computer side of it so there would have been extra pins for that purpose. Maybe they had thought at one point about their own tape deck? Sadly, I don't know much bout the 99/4a.



#57 acadiel OFFLINE  

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Posted Fri Nov 30, 2018 2:32 PM

If it's hexbus it's the same just a different pinout

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Nope, the CC-40's processor ROM (2K) doesn't have the cassette routines built in.  Someone would have to figure out how to add them by dumping the CC-40+ 4K processor ROM or extracting them from the TI-74's 4K processor ROM.  

 

To be clear, it probably can do it.  But not without creating some assembly routines.






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