Turnkey monitor via 8N2 Teletype

General discussions related to the Altair 8800 Clone

Turnkey monitor via 8N2 Teletype

Postby mcleinn » June 6th, 2019, 10:32 am

Hello Altair Clone community,

I'm successfully loading into 4K BASIC via paper tape from my Teleprint 390 teletype. So far, so great!

However, I'm having troubles using the Turnkey Monitor.

I can enter M000000 alright, but after typing the first two digits of the octal code, the monitor prints "?" and exits to the "." prompt.
I don't get the same result from the terminal, so I guess it must have to do with the timing of the teletype connection.
Do I need to modify the turnkey monitor? Are there "virtual jumpers" which can/need to be set?

(Also, it seems that the Turnkey monitor assumes 88-2SIO, correct?)

Thank you
mcleinn
 
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Re: Turnkey monitor via 8N2 Teletype

Postby mcleinn » June 6th, 2019, 6:00 pm

I tried a few alternatives and solved the issue by installing the "improved" Turnkey monitor (UBMON) instead
mcleinn
 
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Re: Turnkey monitor via 8N2 Teletype

Postby AltairClone » June 6th, 2019, 8:21 pm

Interesting. I am not able to duplicate your problem running the original Turnkey Monitor with my Altair Clone connected to an ASR 33.

The ? error is given when you type the 2nd digit of the octal value, not the third, right? Can you take a picture of the teletype paper where the error was occurring and post it?

Mike
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Re: Turnkey monitor via 8N2 Teletype

Postby mcleinn » June 7th, 2019, 5:37 am

Yes, exactly, when typing the second digit.

I should add that the issue occurred with the modified Turnkey-monitor TURMONH. I didn't try the original monitor, as I assumed
it would be largely identical.

The TP390 is basically an ASR-33 with an electronic keyboard and a few PCBs, such as a current loop to RS232 converter.
So it might well have a slightly different timing?

Image: https://drive.google.com/open?id=1-DAfW ... mmoVu7o77T

If I may add another question: the teletype's "LINE" light doesn't go on, when connected to the Altair. It lights up when connected to
PC. I assume that's because the Altair Clone doesn't set DCD or DSR lines. Is there a way to do that (or do I need a hardware bridge?)

Thank you
mcleinn
 
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Re: Turnkey monitor via 8N2 Teletype

Postby AltairClone » June 7th, 2019, 9:11 am

mcleinn wrote:Yes, exactly, when typing the second digit.

I should add that the issue occurred with the modified Turnkey-monitor TURMONH. I didn't try the original monitor, as I assumed
it would be largely identical.


Ah, that explains it. When I created TURMONH from TURMON, I had to squeeze every last byte I could find to fit into the 256 byte 1702a EPROM. I made the assumption the ROM would be used with a terminal emulator since you wanted to send .hex files over, so I eliminated the two bytes used to strip the parity bit from incoming characters (since the terminal emulator can be set to no parity). But, your teletype has the parity keyboard which adds a parity bit to each keyboard transmission. Whenever you type a digit which results in the parity bit being set, it will generate the ? and abort.

Mike
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Re: Turnkey monitor via 8N2 Teletype

Postby AltairClone » June 7th, 2019, 9:22 am

mcleinn wrote:If I may add another question: the teletype's "LINE" light doesn't go on, when connected to the Altair. It lights up when connected to
PC. I assume that's because the Altair Clone doesn't set DCD or DSR lines. Is there a way to do that (or do I need a hardware bridge?)


Sounds like the RS-232 to 20ma converter in your TP-390 must use one of the RS-232 lines to illuminate the "LINE" light (maybe DCD or DSR as you mention). The only output other than transmit data from the real Altair is the RTS pin on the 6850 ACIA on the 2SIO board. The same is true for the Altair Clone. In the Clone as shipped, the RTS output from the ACIA is connected to pin 5 on the rear panel DB-25 (see page "C. Serial Port" on page 2 of the Altair Clone manual). You can make an external cable that connects pin 5 to whichever pin you find lights the "LINE" light, or move the wire inside the clone from pin 5 to the appropriate DB-25 pin.

Mike
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