Re: ICD Multi I/O RS232 Port Speed

"phantomm_1" <phantomm@xxxxxxxxxxxxxx> wrote in message
news:4967d166$0$5472$bbae4d71@xxxxxxxxxxxxxxxxxxxxxx

ICD Multi I/O RS232 Port Speed
-----------------------------------

Has anyone tried to upgrade the MIO RS232
hardware for faster Baud Rate?

I know this has been done on other systems,
Seems possible to do a chip replacement.

And probably possible on the ICD P:R connection
too.

28.8 would be good for a start.

And has anyone tried to do anything with the MIO's
Video port?
Surely it could be used for something if it can be
accessed with software.

Also, am I correct that not all MIO's have the Video Port?



The MIO used a 6551 chip.
http://www.westerndesigncenter.com/wdc/documentation/w65c51s.pdf

for the data *** if you want to have a look. While it could have been
easily fixed in silicon by adding an extra divide by register or maybe a
different prescaler, I know of nobody who did it. Maybe you can find some
outfit that did it but I am pretty sure none of the usual suspects modified
an MIO or manufacturer modified the silicon. I was kind of suprised when I
saw ICD used a 6551 myself as it was already considered obsolete when the
MIO came out: More of a quick and dirty hobbiest type chip rather then
something a professional would use. I guess in theory you could do it in a
PLD and adapter for a 28 pin socket but there aren't enough people with MIOs
for it to be anything other then a mental exercise. The data *** suggests
you could just change the crystal i.e. use a 3.68 mHz vs. 1.84 mHz but I
know of no one who has tried this. I did make a cartridge version of a 6551
years ago but it didn't have interupt capability<limit of the cartridge
port> and I never used anything but a standard crystal.

Almost academic in that for doing anything other then blind transfers the
Atari couldn't keep up. Things like file transfers where you weren't echoing
things to the screen would have been fine.

Story I heard on the PR:Connection was ~the micros that went into them were
over runs that a chip manufacturer dumped on the market. Something like 10+
years later FTE still had a pallet of them for sale at fire sale kind of
prices and they still didn't sell them all. The PR:C had on chip ROM and
were ~surface mounted to PC board so it would be near impossible to fix.

With all these older chips and even using SIO2PC is tiny hardware buffer
either on POKEY or the chip itself. More modern chips like the 16550 give
you about a dozen bytes of buffer which gives you a little elbow room to
work. Thing is even those chips are decades old and nobody uses them
anymore. Everyone seems to have gone with those all in one chip sets from
various manufacturers that include IDE, floppy, printer, two serial ports,
???. I remember TI had one you could buy for $10 or so. Unfortunately they
were made for the IBM/Intel style buss so AFAIK nobody adapted them for the
6502 series.

I don't think the ICD/MIO video ever got beyond the design/dream stage. That
is no circuit board or drivers were ever done. Yes, there still are holes in
the Atari memory map that you could hang just about anything on. The
decoding is already on the 74LS138<?> for $D100, $D600 and $D700 pages. No a
huge problem but the MIO takes $D100 page so any expansions have to be
mapped outside that range.

Rick


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