Re: A92: New design-Please Read


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Re: A92: New design-Please Read





JamesL000@aol.com wrote:

> Due to Motorola discontinuing the microproccessor that I was originally going
> to use and someones suggestion to use a PIC microcontroller.  I looked around
> on Microchips web page and found a reasonable good match that runs a lot
> faster(33 MHz).
> Because of this I, once again, redesigned the entire project.  What I am
> going to have is everything designed in a slightly complex modular system.
>  This will allow for future expansion.  I am going to have a seperate
> interface unit that deciphers the TI-protocal, figuring out which type of
> file is being sent, what kind of calculator is sending, and will also have an
> added variabletype that would allow for direct control of the interface by
> allowing seperate control of the datalines.
> I am almost done designing a printer adapter that will automatically print a
> text file when sent to the interface when it is connected, I am also planning
> on allowing for more than one device to be attached at one time because only
> certain ones would respond to certain file type.
> Another possibility is for the interface to detect what devices are attached,
> unfortunatly this would mean that I would have to change the port from a DB25
> to a DB50.
> Planned pinout of DB25F connector on interface:
> 1 /strobe
> 2 D0
> 3 D1
> 4 D2
> 5 D3
> 6 D4
> 7 D5
> 8 D6
> 9 D7
> 10 send/request (for a memory expander)
> 11 text
> 12 program
> 13 function
> 14 string
> 15 data
> 16 expressin
> 17 figure
> 18 matrix
> 19 picture
> 20 list
> 21 macro
> 22 fargo control
> 23 system ready/reset
> 24 +5V
> 25  ground

Don't waste all those bits. If you must use one bit for a control bit, so when
that is enabled all those bits will have values like those. That way you can use
one bit for enabling things like the parrellel port. And some of the pins could
be multiplexed for addressing which memory chip is used for the data. And you
need one to control read/write for the memory chip. Look at a pin out for a ram
chip that will help you find out the other pins you need. And remember you only
get 25 pins, so you do need some of those pins to connect to the TI-92.

And you should have an external cpu for ti protocal if absolutly necesary. I
think that the chip should be an EPROM so I can send it back to you, and you
could reprogram it for a fee so it could have TI protocol.


References: