The ProSys / 1050-2-PC Interface.

Information provided by: Clarence Dyson


This is the circuit that is used by Nick Kennedy (the developer of the SIO2PC software) as seen on his page. It uses a MAX-232 RS232 to TTL level converter and is somewhat more expensive than the 14C89 version below. Either interface will work just fine. I have built all the different interfaces shown on the pages and some not shown. There is little or no performance difference between any of them in normal operation.



Both of these 14C89 interfaces should work just fine. I would opt for the second however as there is a larger current supply to work from. Not that the CMOS chip requires that much. Better still, build the interface into a 810/1050 drive and be done with it. From one to four less parts to play with.

Here is a picture of the first PROSYS Clarence Dyson built. Notice the 7805 regulator. He originaly used a 1489 and couldn't get the zener working so he added a wall wart and the regulator to get 5 volts for the interface. He says he still uses this box as it works very well. It does have a 14C89 in it now and Clarence says maybe he will change it to get it's power from the zener and RS232 port some time.

What is a "ProSys" interface? Again as you can see from the schematic above not all that much at all. Again 4 parts, some wires and connectors. You don't need much as you only will be connecting an Atari disk drive to your PC.

The normal ProSys interface can be either a Atari SIO cable with a RS232 connector and electronics grafted onto one end or an Atari SIO (13-pin) plug and cable on one end, a RS232 (9 or 25 pin) plug and cable on the other end and some electronics in a box in between plus a program called "ProSys" running on your PC.

NOTE: You can eliminate the 13 pin SIO socket and the 9 pin RS-232 socket and save some money (about $4.00). The reason I used then is I didn't want to cut up a SIO cable and I had some SIO sockets in the parts bin.

You can build a ProSys interface for under $12.00 if you have to buy all the parts or under $3.00 if you have a Atari SIO cable.

These Prices are from JDR Microdevices,
QUAD RS232 RECEIVER (75C189) 14P DS14C89 $.89
RESISTOR - 5.6K OHM 1/4W, 5% R5.6K $.05
DIODE - 5.1V 1W ZENER 1N4733 $.17
TANT. RADIAL CAP .1UF 35V(50V) .1LS T.1-35 $.15

NOTE: You can save $8.00 by using a SIO you already have. NOTE: I have seen SIO cables running from $1.50 to $9.00, so look around if you don't have one.

How to build it:

The only connections to the I.C. are to pins 1,3,4,6,7,8,10,13,14. Only pins 13 & 14 are tied together. The .1uf cap is between pins 7 and 14 and should be right at the I.C. or socket. It is for decoupling the I.C. and is important.
This is the SIO plug when looking at the back of the Atari.

The color code for the SIO cable:
Black (pins 4 & 6) or bare wire. Both of these are grounds, one logic & the other shield. If you really want to be sure you have a good ground you can use both of them.
Blue (pin 10) is +5 volts in every cable I've seen.
Green (or Dark Green on cables with two green wires) (pin 5) is DATA OUT.
Violet or Light Green (pin 7) is COMMAND.
Orange (pin 3) is DATA IN.

That's it, 5 connections to the Atari serial cable, 4 to the IBM serial cable, 1 chip, 1 diode, 1 resistor and 1 cap. The IBM connector will have the numbers on the plastic, but you may need a magnifiying glass to see them.

Sio Orange  (Sio Pin  3) -> 1489 Pin #10
Sio Black   (Sio Pin  4) -> 1489 Pin #7
Sio Purple  (Sio Pin  7) -> 1489 Pin #3
Sio Green   (Sio Pin  5) -> 1489 Pin #6
PC Ground   (9p #5) (25p #7 ) -> 1489 Pin #7
PC DTR      (9p #4) (25p #20) -> 1489 Pin #1
PC RXD      (9p #2) (25p #3 ) -> 1489 Pin #8
PC TXD      (9p #3) (25p #2 ) -> 1489 Pin #4
If you need help in building the ProSys Interface, you might look into a local Amateur Radio Club, Junior College Electronics Class or High School Electronics Class.

Where to Get the Software:

You can get the directions to build the APE cable here APE and download the software here Atari Peripheral Emulator
You can get the directions to build the SIO2PC cable here Nick Kennedy's and download the latest software here SIO2PC For more information about these interfaces visit the author's web sites.

Comments, Questions, Click Here.

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