Altair Replica and Stuff

[TomL_12953]

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.

[Geoff Harrison]

Originally Posted by TomL_12953

Did you have a 20mA machine there to test Port 0? If so it worked for you, right?

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.

[phe]

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

[TomL_12953]

Originally Posted by phe

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

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

[phe]

Originally Posted by TomL_12953

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.

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

[TomL_12953]

Originally Posted by phe

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.

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

Tom L

[n0jcf]

Originally Posted by phe

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?

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

[TomL_12953]

Originally Posted by n0jcf

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.

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

[Grant Stockly]

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

[TomL_12953]

Originally Posted by Geoff Harrison

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.

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?