Altair Replica and Stuff
 

The computer itself is performing flawlessly. The 2SIO, Port 1 is perfect. I hooked it up to a terminal program on a PC and can run VTL-2. That's a neat language for taking so little memory. On Port 0, though, the Teletype prints the OK message but I can't type anything. I checked my cable wiring about thirty times then hooked the Teletype up to the PC and was able to communicate with the Altair32 emulator and a terminal program OK so I know the Teletype is good. Any ideas what could be wrong? Did you have a 20mA machine there to test Port 0? If so it worked for you, right? Thanks again for your obvious care in the assembly and packing of this machine. I can't wait to get the Port 0 problem fixed and to get my ACR board from Grant.

No, unfortunately I don't have any current loop devices. I did verify that the 6850 was working correctly by connecting a TTL/RS232 adapter to its Tx/Rx pins, so if there's a problem it must be with the 7404 inverter (IC K, pins 8,9) or something on the incoming side (pin 9) of that. Do you have any way of testing whether a reasonable signal is getting to pin K9?

Geoff.

Hi Guys. I did not get my teletype working, but now you have inspired me. Sorry, Tom, but I cannot help you yet but perhaps I can if I get mine working.

My problem is that I do not know if my teletype is current loop or RS-232. Do either of you know how I can figure this out? Are there pin voltage settings I could measure? I've always held off because I did not want to take any chances of frying my 2SIO port or my teletype. Would a wrong (mismatched) connection cause harm?

Paul

Unfortunately, being a software person, I wouldn't even know what a reasonable signal is. Since the 7404s are socketed, would it help if I swapped them and see if the problem follows the current K chip?

2SIO Failure
 

Well, I swapped the two inverters. The problem stayed where it was, the first port only. So both inverters are good. (You probably already knew that.) Where do I go from here?

TIA

Tom Lake

Tom,

You said earlier that you checked the teletype by connecting it to a PC. Does that mean you have a current loop port on your PC?

Geoff.

Yes. I have an Advantech PCI-1603 2-port PCI board where either port can be configured as either RS-232 or 20mA Current Loop (sound familiar?) by setting jumpers on the board. I bought it specifically to run the Teletype with the Altair32 emulator until I could get Grant's replica. It works great!

BTW are there instructions somewhere for using the monitors, DBL, MBL and music ROMS I got with my system? I tried to load 4K BASIC into the replica using your instructions for the TeraTerm terminal emulator but have been unsuccessful. If I could use the MBL ROM to do it, I'd save having to enter the bootloader each time That's the point of the MBL ROM, no? 8^) Thanks again for your patience!

Tom L

You can check it without connecting it to your Altair. Plug in the Teletype to the AC outlet. Turn the Line/Off/Local knob to Line (all the way counterclockwise if you don't have the front aluminum escuheon). If the TTY starts chattering without printing anything, it's 20mA Current Loop. If it stays silent, it's RS-232. Here's another tip: Don't leave the Teletype plugged into the power line when not using it. Even when off, there's a board inside that stays powered on and gets hot enough to scorch the plastic case. It will significantly shorten the life of your unit.

Tom Lake

I'm not sure how to use the AdvMon. I got it to respond to 5 commands: Mxxxx, Wxxxx, Exxxx, Rxxxx, Gxxxx, where xxxx is a 4 digit hex address. The only one that did anything useful for me was M which displays a hex dump starting at xxxx, one line at a time. Press space for another line, return to quit.

Yes, you definitely want to use MBL instead of toggling a loader in each time. I tested the PROMs on your machine with my 2SIO and got 4k basic to load. You have to play some games with the front panel switches because 4kBasic interprets the sense switches differently from MBL, but it's still easier than entering a 1st stage loader each time. We can go over that when we get the port working.

Just out of interest, did you try entering the simple echo routine on http://www.solivant.com/altair_bootl...oaders&pagen=1 ? If that won't work correctly we're not going to get VTL, MBL or anything else working on that port.

Geoff.

I tried it, just to see if my input problem on port 1 is a hardware problem or a problem with VTL-2. It's a hardware problem. I can't use the first port for input. If I change the IO port references iin the code to the second port, it works OK.

Tom L

How? I tried examining its start address and executing from there but I can't get output at all. How do you specify port 2 rather than port 1? As you know I can't type on port 1.

Tom L

I don't know if you can. Like MBL, it may be hard coded to port 1.

As for your current loop problem, I'm not sure what else to suggest other than sending the card back and I'll do my best to figure out what's wrong with it.

Geoff.

2SIO Woe
 

OK, I was hoping to avoid that but it does seem like it's the only way, given my poor hardware skills. I'll try to get it out tomorrow. Did you include your address on the box? I'm at work right now so can't look at it and of course I was too excited when the box came to check for such details! If you want, send me your address privately.

Thanks, Geoff.

My address was on the box and I also just sent you a PM.

Geoff.

Thanks, Tom. OK, I have RS-232. Thanks for helping me figure that out. But it means that I can't try to replicate your setup on my equipment or offer any helpful suggestions. I'll just fade into the woodwork now..... Sorry for interrupting your thread.

Paul

Hey, no problem! You're lucky to have one of the RS-232 models. Much easier to interface with modern equipment.

Tom L

tty
 

Hi Tom L
I will suggest some things that you can check before sending the board back to Geoff, Most of it is elementary, But that is what usually can trip one up...
trade the 6850's and see what that does, also check for bent pins--
check all Ic's for bent pins..
check that all the resistors , diodes, caps and transistors are in the ccorrect holes and well soldered on both sides...
check that you have it wired right between the jumpers and the connector ( signal table for tty)
switch port 0 to an rs232 and wire accordingly and see if it works as an rs232. then get it to work as an rs232 or if it works switch it back to tty...
that's all I can think of for now....
THANK YOU Marty

If it is a genuine Teletype model 33, then it is 20mA. Teletype did not build any model
33 with RS232. They were all current loop. It would only be RS232 if there was a
current loop to RS232 converter installed inside or outboard somewhere.

Teletype model 43 is possibly RS232... but this is a much more modern "teletype" and is mostly electronic (with dot matrix printhead) rather than the nearly all mechanical model 33.

Chris

Most people didn't buy directly from Teletype Corp. and independent vendors frequently installed an RS-232 interface converter internally at the request of the customer. I'm surprised that, even though the ASR-35 was much more rugged than the 33, many more 33s survive today than 35s (at least on the used market). I suppose it could be because so many more 33s were sold, though.

Tom Lake

What is the current status of the 2SIO? Do you still want me to mail you mine or is Geoff modifying it for 2 RS-232 serial ports?

The other undocumented chip is the MUSIC ROM. Just examine and run at the address of the ROM. It will load the listing byte for byte (from the newsletter) into memory starting at 0000 and begin playing.

I will send the VTL-2 manual to Geoff and Tom.

Here are instructions for the advanced monitor:

;
; Hardware Debug Monitor for 8080/8085/Z80 processor family
;
; This simple monitor requires NO RAM of any sort. You can use it to
; poke around the system as long as the CPU, a ROM and the UART are
; working. (Hint: if the UART is not working, you can use the polling
; by HDM80 to track down its accessing and debug it).
;
; This monitor provides basic read/modify memory, as well as
; Loop Read/Write functions (useful when hardware debugging).
;
; Commands (must be UPPER-CASE):
; Mxxxx - Display memory at specified address
; Displays one line, enter SPACE for another, RETURN to stop
; Exxxx - Edit memory at specified address
; Prompts with location, enter two digit HEX value, then
; SPACE to proceed to next or RETURN to stop
; Gxxxx - Go (Begin Execution) at specified address
; Rxxxx - Perform Loop-Read at specified address (RESET to stop)
; Wxxxx dd - Perform Loop-Write dd -> specified address (RESET to stop)
;
; Build with DDS XASM tools:
; MACRO HDM80.MAC >HDM80.ASM
; ASM85 HDM80 -t
;
; Dave Dunfield - Aug 4, 2007
; Grant Stockly - Nov 22, 2007 - Modified for 2SIO at 0,1
; GETC modified
; PUTC modified
; HINT modified
;
;
cStat EQU $10 (020) 2SIO Status Register
cData EQU $11 (021) 2SIO Data Register

2sio
 

I just sent the board back to Geoff to convert back to RS-232. I gave up on TTY simply because if my Teletype breaks down, I won't be replacing it and will need port 0 to be usable by more modern terminals. I have an RS-232 to Current Loop converter I can use to drive my Teletype for now. Also, I'm bidding on an SIO-C TTY board on eBay so if I get that, I can use that along with the 2SIO.

Any idea about how long it'll be before you can ship the ACR cassette board pair to Geoff for assembling?

Another thing: I have a 64K static RAM board which seems to be working fine so you don't have to bother sending that 64K board you said you'd throw in the deal.

Would you have and spare 10-pin female Molex connectors (and metal inserts) I could buy? If not, what's the Molex part number and where do you get them?

Thanks for your time.