Re: A92: New design-Please Read
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Re: A92: New design-Please Read
>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.
Good idea with the multiplexing, this will help later on. as far as only
having 25 pins, I changed that to a dual-row 40-pin right-angle header
strip(identical to the one on an IDE interface), this will allow for a few
more lines, it also makes it a little easier to stack the devices. As far as
the lines hooking up to the 92, the PIC already has two USARTs that can deal
with the link, the PIC has 7 IO ports which allow for three to be used in the
interface, one to hook up to the 92, and one or two for switches and/or
indicators. The PIC also happens to be an EPROM, this will probably never
get to be of a large enough scale for masked-ROM chips to be worth it. I am
nearly finished with the PCB design, unfortunatly I am using the demo version
of a really good PCB designer program, which means that I cannot directly
print the PCB design, I have to indirectly print it through something like
PaintBrush(ack..). I was wondering if anyone has the full version of the
"PCB designer" by Niche software so that I can get a good printout of the
PCB.
-James