Altair Replica and Stuff

[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]

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.