D I S C L A I M E R I have tried to ensure that my software is free of harmful defects (bugs) and of viruses. However, either could slip through my defenses. Use the software at your own risk. Similarly, I believe my hardware design to be in accordance with good practice, and I have a number of satisfied users. However, wiring errors, errors in my design, and configuration differences are possible and I cannot guarantee that these problems will not lead to damage to your equipment or software or other unforeseen damages. Furthermore, if you choose to construct my interface yourself, you must be experienced with electronic building techniques. Even if you are experienced, you could burn or cut yourself or experience other damage or injury. So attempt building the device at your own risk. I consider the SIO2PC system to be a service to the Atari user's community. Although I ask a shareware contribution, and do make a charge for assembling interfaces or kits, I still consider my efforts to be a hobby and a service. IF YOU HAVE SENT ME ANY PAYMENT FOR ANY SOFTWARE, KIT, OR ASSEMBLED INTERFACE AND DO NOT WISH TO ASSUME FULL RESPONSIBILITY FOR USE OF OR CONSTRUCTION OF THESE ITEMS, YOU MAY RETURN THEM TO ME AND I WILL REFUND YOUR MONEY. IF YOU ARE CONSTRUCTING THE INTERFACE AND CANNOT VERIFY THE ADEQUACY OF THE DESIGN ON YOUR OWN, SEEK THE ADVICE OF ONE COMPETENT IN ELECTRONICS. OTHERWISE, DO NOT ATTEMPT TO BUILD AND USE THE INTERFACE. BUILDING THE SIO2PC INTERFACE BACKGROUND ON HARDWARE REQUIREMENTS: The RS-232 serial port on your PC and the SIO serial port on your Atari 8 bitter are quite similar. There are some differences, however and the SIO2PC interface is designed to accommodate these: 1) The Atari puts out (and expects as inputs), TTL level signals. In general, +5 volts for logic 1 and 0 volts for logic 0. The RS-232 standard is bipolar: roughly +5 to +15 for logic 0 and -5 to -15 for logic 1. Note that this is also inverted from TTL, that is, the more positive signal is logic 0 here. So, the first hardware requirement is to convert TTL to RS-232 levels for signals from the Atari to the PC, and RS-232 to TTL levels for the reverse direction. 2) The RS-232 standard is designed for one to one communication. The "data out" line of one device goes to the "data in" line of another, and vice-versa. The Atari SIO system is a data BUS. The Atari computer's data out line can connect to several peripherals, and their data out lines all connect to the one data in line on the Atari computer. This means there is a potential for interference if more than one peripheral tries to talk at the same time. This is solved by simulating an open collector output to the Atari using a diode and pull up resistor. 3) Handshaking. The Atari uses only one handshaking line on its SIO bus. This is called the COMMAND line. The Atari computer uses it to tell all peripherals to "listen up" because a command to one of you will follow. The PC's serial port has several handshaking lines, so the interface will just convert the COMMAND line's TTL level to RS-232 and send it to the PC's "RI" handshaking line. 4) Baud, Word Size, Start/Stop bits, etc: The philosophy of SIO2PC is to require no software patches on the Atari. This is so you can BOOT the Atari from the PC, you can use any DOS, there will be no software conflicts, etc. Fortunately, we got lucky here. The Atari serial bus runs at 19,200 bits per second. The PC's BIOS doesn't allow speeds this high, but the hardware does, so the SIO2PC software just programs the chip directly without DOS or BIOS. The other parameters listed are also easily programmed into the serial chip (UART) on the PC by software. So, if we just handle 1 thru 3 above, we are set to go with regard to hardware. CIRCUIT DETAILS: I now have files which draw the schematic on your PC screen using built in ASCII symbols. This means you don't need any special viewer program to see them. The files are 1SIO2PC.ASC, 2SIO2PC.ASC, and 3SIO2PC.ASC. Each takes up one screen. The batch file VIEW-CKT.BAT displays the three on screen in succession. You can also dump these files to your printer. Also note that I have .GEM (for PC) and TurboCad files which draw less clunky versions of the same thing, plus a board layout using a Radio Shack prototype board. Write me for copies. Chip used: 1) The Harris ICL232 (or MAXIM MAX232) is a single chip RS-232 to TTL and TTL to RS-232 converter. It includes two gates to convert TTL to RS-232 and two to do the reverse. The beauty of this chip is the internal 5 volt to bipolar power supply converter. Normally, you would need a separate plus and minus 12 volt or so supply for the RS-232 levels, but this chip takes the 5 volt supply (from the Atari) and generates all the voltages needed. CONNECTOR INFORMATION: Most PC serial ports use a 9 pin connector known as a DB-9. The connector has male pins. Therefore, the connector you put on your interface connector should be a DB-9F, with sockets. This is the view of the connector on the computer. It is also the view of the rear of the DB-9F connector (the end you solder the wires to): 1 2 3 4 5 6 7 8 9 The Atari serial port uses a specialized connector which I haven't found anywhere else. Looking into the jack on the computer, it looks like this: 2 4 6 8 10 12 1 3 5 7 9 11 13 You can get the connector itself from Atari parts suppliers. However, I prefer to buy an I/O cord with connectors on both ends and cut it in half. Then you can use an ohmmeter to find out which wire is wired to which pin. 25 Pin Serial Port Connector: Many PC serial cards use a 25 pin connector instead of a 9 pin. Here are the equivalent pins if you have the 25 pin: DB-9 DB-25 2 3 3 2 5 7 7 4 9 22 PARTS LIST FOR SIO2PC KIT _____1 - BOX, /w LID, SCREWS (R.S. 270-220, 4 X 2 X 7/8) _____4 - 22 uF ELECTROLYTIC CAPACITORS, 25 volt _____1 - 0.1 uF DISK CAPACITOR, 25 volt or more. _____1 - INTEGRATED CIRCUIT, I.C. # 2 (ICL-232) _____1 - SIO CABLE & CONNECTOR (Atari I/O cable cut in 1/2) _____1 - 5 CONDUCTOR CABLE _____1 - DB9F OR DB 25F CONNECTOR (as req'd for your PC) _____1 - CONNECTOR HOOD _____1 - CIRCUIT BOARD (R.S. 276-150) _____6" - BARE WIRE _____6" - INSULATED WIRE _____1 - 16 PIN IC SOCKET R.S. means Radio Shack. You can get most of the common stuff from there. I drill a hole in each end of the box and install grommets (from Radio Shack) in them. Then I feed both cables thru the grommets before connecting them to the board. I put the board in the box component side down. Note: this board is almost a perfect fit in this box, but actually is a bit snug. I take a file and trim 1/16" or so off the long side before working on the board. Or, you can use the next larger size box. OTHER COMPONENT SUPPLIERS: The only slightly difficult to find part is the ICL-232. You can get it (or the MAX-232) from: DIGI-KEY 701 Brooks Ave. South P.O. Box 677 Thief River Falls, MN 56701-0667 800-344-4539 or 218-681-6674 or JAMECO ELECTRONICS 1355 Shoreway Road Belmont, CA 94002 415-592-8097 or B.G. Micro, Inc. P.O. Box 280298 Dallas TX 75228 1-800-276-2206 214-271-5546 The above suppliers will also have the capacitors & connectors. For the Atari I/O connector or cable I use: AMERICAN TECHNA-VISION 15338 Inverness St. San Leandro, Calif. 94579 510-352-3787 For Atari parts, also see: B & C Computer Visions 3257 Kifer Road Santa Clara, CA 95051 408-749-1003 and Best Electronics 2021 The Alameda Suite 290 San Jose, CA 95126-1127 408-243-6950 If you want, you can contact me about parts. I'll currently supply a kit of all the parts listed plus drawings and instructions for $30 plus $5 P & H. I'll build and test it for another $20. If you go this way, I don't expect additional "shareware" payment for the software. DISCLAIMER/WARNING!!! As of this writing there are around 100 known users of this software and interface, all having satisfactory results. However, unless you feel comfortable with building circuits and interfacing computers, I don't recommend trying it without help. Likewise, errors are possible in my above circuit description. I must insist that you assume all responsibility for equipment damage or personal injury if you decide to build and use my system. I recommend getting the data sheets for the chips and seeing for yourself that the pin numbers I give match up with the mrgr's description. In general, the inputs and outputs of both the Atari and the PC serial port are fairly resistant to damage from inadvertent grounding, connecting two outputs together, etc. However, your system may turn out to be the delicate one. Note: the negative going output of the RS- 232 port stands a good chance of DAMAGING any TTL input it is connected to. In other words, the RS-232 to TTL conversion performed by the ICL-232 chip is absolutely necessary. On the software side, I have taken pains to ensure against damaging your files. For instance, I only use DOS calls, I don't do any direct disk sector writes. But the PC is a complex beast, file outputs can be redirected, resident programs can clash in strange ways with TSRs, etc. So, please use this program at your own risk. If you're building it yourself, also see the KIT_G.PRN file for a detailed, wire by wire checklist of instructions. KIT_G.PRN should be copied right to your printer, but you can also view it on screen. If you have problems, use the diagnostic software now included with the package. Read DIAGS.TXT on your distribution disk.