Question about wiring rs232 cable for 882SIO board
I'm working onthe 2SIO board and trying to figure out how to wire the molex connector to the 25 DB female connector. I cannot figure out how to match up the pins. In the MITS manual I have, it is supposedly described on pages 28 and 29.
Page 28 describes the molex connector. It refers to pins 1, 2, 3, 4, 7, 8, and 10. I'm guessing that page 29 describes the 25 DB connector (it is not labeled). It refers to pins 2, 3, 4, 3, 8, 20, and 7 The problem is that page 28 shows 2 grounds while page 29 shows only 1, and page 29 shows a DTR on pin 20 and page 28 has no corresponding pin. Any ideas? Paul |
Hi Paul;
I did this awhile back, and ran into the same problem :( Here is what I did, and I got it to work with my PC. Since I am not at my place and am out of town for another week or so. I can only tell you what I did remotely, and with a bad memory, mine , not the computers. I assume for now that you are using your PC with Hyperterminal. I looked up rs-232 on the WEB, and looked for 9 pin to 25 pin, and used modem half duplex one way and full duplex the other. The full duplex is from the Altair to the Pc and the half duplex is the other way. Since the 2Sio Board doesn't provide a full duplex both ways. I should be something like this -- I am doing this from memory, so I might be wrong. connect the following -- 2 (on the 25 pin) to 3 (on a 25 pin) or its equivalent on the 9 pin 3 "" to 2 "" "" 7 "" to 7 "" "" (and I think the following) 4,5,8 "" to 20 "" "" 20 "" to 4,5,8 "" "" ( I know pins 4 or 5 possibly may not be right) and on the Pc to the Altair side as you said it doesn't have 'DSR' So it can't be connected. If you need more help, I can look it up on the web and tell you almost for sure which ones to use. Or wait until I get back home and I will see what my machine has wired up. Thanks Marty :) :) :) |
Thanks Marty, but I think you answered the question that I would have asked pretty soon. I think you are describing the wiring between the 25 pin connector on the Altair and the 25 or 9 pin connector on my PC. Yep, that would have been a question I would have had to ask. :eek:
But I'm a step before that. I'm trying to figure out the wiring inside the Altair case, between the 10 pin Molex connector that attaches to the 2SIO board and the 25 pin connector that I am going to mount on the back of the Altair case. Give your explanation of what happens outside the case, I may be able to figure out the wiring inside the case. But please do look, when you get home, at that part of the wiring inside the case and let me know what you did there. I’d appreciate it. It seems that you keep bailing me out, Marty. I sure appreciate it! :D :D I hope to return the favors some day. Paul |
Hi Paul;
You are right about the manual pages. :D :D I had to Download it to this computer, ( I have all of these files on my machine at home and my download to this machine came by a slow boat through China.) :( so yes -- pin 1 on the sio board to pin 5 of the rs-232 2 " 8 " 3 " 4 " ( and 20, I think) 4 or 10 " 7 " 7 " 2 " 8 " 3 " 10 or 4 " 7 " What I did to first try it out and make sure I was right ,, was to use wirewrap wire and just wrap the wire onto the 2-sio board connection and soldered it to the rs-232 connection on the other side to make sure it works. Before pinning the wire on the 2-sio side. Then bring up Hyperterminal and see IF it works, if not then make modifications. (by slipping wires on and off of the pins on the 2-sio) Hyperterminal will let you know when it is happy with the connection. THANKS Marty :o :o |
Hey Paul. I took notes when I wired mine. Here are the notes with pictures of my card below.
I THINK I wired both of my ports for RS-232 hardware handshake but did not connect the hardware handshake wires for port 0 that would keep the card from working without hardware handshaking. Basically, the hardware handshaking is disabled with an easy way of adding it in the future. You should be able to use the pictures of the DB25 connector on one end and the molex on the other to figure out how I wired it. The ribbon cable is junk. :mad: Basic Tx/Rx/Gnd Serial Configuration: D3 to I4 - Port 0 Receive I3 to S1-7 - Port 0 Receive D5 to N4 - Port 0 Transmit N3 to S1-8 - Port 0 Transmit S1-4 to S1-10 - Port 0 Ground E3 to J1 - Port 1 Receive J2 to S2-7 - Port 1 Receive E5 to N6 - Port 1 Transmit N5 to S2-8 - Port 1 Transmit S2-4 to S2-10 - Port 1 Ground Hardware Handshake: D2 to I7 - Port 0 Clear to Send (D2 end NOT connected) I8 to S1-1 - Port 0 Clear to Send D1 to I5 - Port 0 Data Carrier Detect (D1 end NOT connected) I6 to S1-2 - Port 0 Data Carrier Detect D4 to N2 - Port 0 Request to Send N1 to S1-3 - Port 0 Request to Send E2 to I2 - Port 1 Clear to Send I1 to S2-1 - Port 1 Clear to Send E1 to J3 - Port 1 Data Carrier Detect J4 to S2-2 - Port 1 Data Carrier Detect E4 to N8 - Port 1 Request to Send N7 to S2-3 - Port 1 Request to Send These are big pictures, so hopefully no one with a modem will try to load the page. :) http://www.stockly.com/images3/07090...cable_3181.jpg http://www.stockly.com/images3/070909-DB25-1_3182.jpg http://www.stockly.com/images3/070909-DB25-2_3183.jpg |
THANK YOU Grant you always come through :D :D :D
I can even use these to check mine :p :p Marty |
Any updates Paul?
Grant |
Well, after a long time away from the hobby due to extensive priorities at work, I'm back at it again. The diagram you posted, Grant, was extremely helpful. I have the board all wired and "almost" all the ICs in. There are two ICs that are a mystery, and rather than try hit/miss I figured I'd ask here first.
In the MITS intructions, page 3, IC G is defined as a 93L34 and IC F is simply defined as a 16 pin socket. Lovely. In the kit I have two ICs left over. One is marked GD4702B and the other is marked 74LS259. Any idea whic is G and which is F? I'd like to get this board working! Once I install the last two IC's, what's the best way to test? Is there a preferred loader program, or otherwise, that I enter in via the switches that will at least display something on the RS-232 terminal? Thanks guys. Paul |
Do you remember the e-mail I sent you on 7/20 with the 600 DPI scan of my card! ; )
The GD4702B chip is the chip called "4702". The 74LS259 is a LS TTL version of the 93L34. Here is a link to a scan of the complete card. Its a pretty big picture! http://www.stockly.com/images3/090720-88-2SIO%20Replica%20Prototype%20Top.jpg |
The first program I ran was one that would "echo" all characters sent to the Altair. If you typed "Hello" into the Altair, it would print "Hello" back as you typed.
The next step is getting 4k basic to run. I will try to get you a good memory image and some instructions on that. I won't be able get you anything until Saturday or Sunday. But you should be able to keep busy until then. |
Hi Grant;
I would be interested in the above listing and programs. Thank You Marty:D |
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Paul |
Interestingly I've searched the web for altair programs and found nothing useful. I find that pretty amazing. Well, I've written a number of programs already using the switches, so I took a crack at my own echo program. I would have guessed the program to echo characters would be:
IN 11 011 011 021 00 010 001 OUT 11 010 011 021 00 010 001 JMP 11 000 011 0 00 000 000 00 000 000 So I keyed this in via the switches and then tried every possible configuration of windows hyperterminal I could think of, all 9600 baud, with various partty, flow control, and stop bits settings. I've tried it with and without a null modem cable. No go. Either my program is wrong (highly likely because I used port 021 which is for data and not port 020 which is for control). But I can't find decent descriptions of how the IO ports actually work. I wonder if the documentation was easier to come by in 1975. Or you could just attend the local computer club group. Paul |
You have to reset the port and send a config byte. You also have to check if there is data waiting in the chip buffer before you try to read the serial chip.
You SHOULD check to make sure that the TRANSMIT buffer is empty before transmitting a byte, but for this test we can assume that since you first have to wait for a byte that there will be more than enough time to transmit it before a new byte has been received. Do you understand that? Here is a sample program I just wrote. Sometime saturday night I'll get the program from my S-100 book to you. Code:
;Serial echo program for the 8080 and 2SIO |
ECHO Program
Hi Paul;
I Don't have my notebook here with me, So I had to look it up on the net !!! I didn't take the time to look at all there was, but this should get you started. 000 333 input 001 000 or 020 or what ever port you have 002 017 003 332 004 000 005 000 006 333 007 001 or 021 or what ever port you have 010 323 011 001 or 021 or what ever port you have or 377 if you want to use the sense switches. 012 303 013 000 014 000 (This is in octal) Good Luck Marty :D |
H in the above program means "hex", don't treat those values as octal! :)
Back in the old days there were magazines and journals for programming help. Programming a computer was just the way you did things. There was basic, but in the earliest days no one even had that! So in order to survive you just had to learn it by whatever way possible. The most exciting thing about the kits that I build is the idea that I'm helping preserve some of the knowledge and allowing people to experience these things! |
Marty, you should initialize the port first. It may happen that sometimes it works but that could be just luck. You can't ever count on things being right inside the chips. ;)
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yipee!!!! My card works. I tried your program, Grant. Here are the octal codes for it (assuming you start it at 000):
000 076 001 003 002 323 003 020 004 076 005 025 006 323 007 020 010 333 011 020 012 346 013 001 014 312 015 010 016 000 017 333 020 021 021 323 022 021 023 303 024 010 025 000 I have not tried your program yet, Marty. I'll give that a go tomorrow. Thanks, guys! Paul |
Now, even though you were basically doing what a robot could do...building the board...doesn't it just give you a great feeling of accomplishment!?
When that thing is booting basic using your several thousand solder joints all the pain and suffering will have been worth it. :D:D:D |
Paul, what kinds of other programs have you made? What resources did you used to do it? Any tips and hints for other people in your situation? :)
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Paul |
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All that was pretty boring and I don't really have any tips to offer. I made lots of mistakes in loading the programs through the switches. I played around with the am radio program and made a few different tunes, including the first half of Happy Birthday. I would recommend anyone who has a musical ear try that one. I would key in the song data, run the program, hear any notes that were not right, and quickly fix just the relevant notes until the pitch was correct. Musical trial and error. Perhaps now that I understand how to input data from the serial IO card I will try to capture the keystrokes that come in and store them in memory somewhere to create the tone sequences for songs instead of manually loading successive memory locations with the relevant values. It is probably even straightforward enough to make the altair play tones as I press keys and I might try that as well. These are just some ideas to get some fun out of the work done so far. Nothing earthshattering, just basics. Paul |
Echo
Hi Grant;
I didn't realize that I needed to do that, and I just copied the program out of 'computer notes' Thanks for correcting me, :D I'll have to try it next time when I get to my machine. Paul, Add the initialization part to the top of the program that I had for you. And see if it works. ;) Thats probably why my board sometime worked and sometimes didn't. :o Thanks Grant, Again !!!! :D |
Echo
Hi Paul;
There is a musical program from Dr. Dobbs, that I have at home, which works from the sense switches, I'll try to get it for you the next time i'm home. and here is the origional program from computer notes, I think it has some ERRORS in it, but it should point you in the right direction. Also I know there are some articles about the 88-sio and the 88-2sio, somewhere in the 'computer notes' ,, I just didn't have time to locate them last night. This came from 'computer notes vol 1, issue 6. 000 333 001 000 002 017 003 332 004 000 005 000 006 333 007 001 010 062 011 040, this can be anywhere you want in memory 012 000 013 333 014 000 015 007 016 332 017 012, I think this should be 013 020 000 021 072 022 040 , this can be anywhere you want in memory 023 000 024 323 025 001 026 303 027 000 030 000 There were some other programs in this article that I didn't copy. Have a good time, Thanks Marty :D |
From the book:
Echo routine for the Altair 8800 computer to communicate with a serial terminal via the 88-2SIO. Page 140 of "The S-100 Bus Handbook". 000 : 076 001 : 003 002 : 323 003 : 020 004 : 076 005 : 021 006 : 323 007 : 020 010 : 333 011 : 020 012 : 017 013 : 322 014 : 010 015 : 000 016 : 333 017 : 021 020 : 323 021 : 021 022 : 303 023 : 010 024 : 000 |
echo program
Hi Paul;
I Just found and copied the same program for you from vol. 2 issue 2 of the computer notes. Also vol .2 issue 1 has some information. Thanks and have a good weekend Marty:D |
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