Notes on 1050-2-PC:

I've had a few people ask me about making a device which would allow 
the PC to plug directly into an Atari drive.  After considering whether 
there would actually be any advantages, I've started work on a variation 
on SIO2PC I've cleverly named 1050-2-PC.  (No, it's not limited to just 
1050 drives.  810's and any other Atari drives which accept the standard 
SIO commands can be accessed.)

Hardware Considerations:

1050-2-PC requires a different hardware interface, or at least a 
configurable version of SIO2PC.  The reason is that the DATA IN and 
DATA OUT pins on the Atari computer are swapped on the disk drives 
(and other peripherals).  This is so DATA IN on the computer will go to 
DATA OUT on the peripherals, etc.  Also, the COMMAND line is an 
output from the Atari computer, but it is an input to the disk drive.  So, 
what do we have to do to make an SIO2PC type device properly connect 
to an Atari drive?  Well, first you just swap the DATA IN and DATA 
OUT wire connection points inside the blue box for the Atari (SIO) cable 
only.  The COMMAND line is a bit more complicated.  In SIO2PC it 
uses a gate which converts TTL to RS-232.  It will now need an opposite 
conversion, RS-232 to TTL.  (Such a gate now exists within SIO2PC as a 
spare, if you have the "onechip" hardware.)   And, a different 
handshaking line from the PC is needed.  Currently the RI (ring indicator) 
line, which is an input, is used.  The new hardware will use the RTS line, 
which is an output.  

That pretty well takes care of switching the signal lines, but there's 
another problem.  SIO2PC is powered by the 5 volt line coming out of 
the computer.  The disk drive doesn't put out 5 volts.  So, a separate 
power supply is needed.  Keep in mind that the PC will be playing the 
role of an Atari computer in controlling the SIO bus.  So a real Atari 
computer can't be plugged in to the daisy chain while all this is going on.  
It's strictly one-to-one.  My unit will be powered from a 9 volt battery, 
regulated down to 5 volts.  As I've said before, I'm strictly a hobbyist and 
am not about to sell, give, or otherwise convey anything to people which 
they are going to plug into a 120 volt wall outlet!  

(If you do decide to build something yourself on your own and run it off 
of a 5 volt "wall charger" type adaptor, here's something to consider:  
Most of these units put out rated voltage at rated load (current), but much 
higher voltage with low current draw.  So unless you're sure you have a
regulated adaptor, put a 5 volt regulator on your board.  The MAX-232 
gives 5 volts as the nominal supply voltage and only 6 volts as the 
maximum allowable (more may cause damage).  Not very forgiving!  
Also, most of these little supplies aren't filtered either.  Put an electrolytic 
capacitor across the adaptor's output (say 50 to 100 uF, 25 volt) and a 0.1 
uF disk and 10 uF or so electrolytic across the output of the regulator.  
Again, attempt only what is within your range of competence.  Get 
professional advice or assistance if necessary.  I am not advising anyone to 
build anything!)  (If you are adding a power supply to a unit I built, note 
that I already put a 5 V regulator in it.  So use something that puts out in 
the 9 to 15 Volt range.)

Another note: On a 1050-2-PC, there should be no need for the blocking 
diode and pull-up resistor simulating open collector or Tri-State, since 
multiple devices won't exist on the bus during use of this function.




Implementating the hardware:

I've considered a number of methods.  Currently, I'm working with an 
entirely separate device.  One could also modify SIO2PC using a 3-pole, 
double throw switch and adding a 5 volt supply.  Another method would 
involve having a "two headed" SIO2PC.  It would have one SIO 
connector coming out for connection to an Atari computer and another 
for connection to an Atari drive (not both simultaneously).  

Software:

The intent is to make some software which will allow copying specific 
sectors or entire disks directly to PC disk image files.  I don't know 
whether I will get around to "file-at-a-time" extractions or not.  That 
practically requires writing one's own Atari DOS, or a number of 
DOSses, if you want SPARTA and other types of extractions.

It almost seems to be not worth the effort to do all this, since files and/or 
complete disk images can already be transferred using SIO2PC and an 
Atari computer as an intermediary.  However, I've gotten interested again 
in trying to provide a method of emulating copy protection, so copy 
protected files can be copied and run "un-cracked."  The 1050-2-PC can 
be very useful to analyze disks for copy protection methods.  My intent 
isn't to encourage piracy, but to allow owners of Atari software to run it 
using modern hardware.

I am building the 1050-2-PC functions into a sub-menu of SIO2PC.  
Select main menu choice A followed by sub-menu choice D.  Currently, it 
will copy complete 720 or 1040 sector disks or copy any number of 
consecutive sectors the user asks for.  I will be adding "analysis" of sector 
status and other stuff in the near future.  Also, writing sectors or entire 
disks will be included.

If you're interested:

As I said, routines to copy disk images and sectors are already in version 
4.0 of SIO2PC.  If you want the hardware, or want to know more about 
modifying what you have ... contact me.

Nick Kennedy