Printer Question

General discussions related to the Altair 8800 Clone

Printer Question

Postby kurthamm » January 30th, 2018, 3:28 pm

This is probably a very simple question, but I always have trouble with printers and flow control. I tried to print a banner on my new printer, but I got a buffer overflow error.

The Altair Clone docs identify this serial pin configuration:
Pin Signal
2 XMT from Terminal (out) to Clone (in)
3 RCV to Terminal (in) from Clone (out)
4 RTS from Terminal (out) to Clone (CTS in)
5CTS to Terminal (in) from Clone (RTS out)
7 Signal Ground

My printer docs identify this serial pin configuration:
1 Chassis Ground
2 Serial Data Out - Asynchronous output data line
3 Serial Data In - Asynchronous input data line
7 Signal Ground
11 and 20 Data Terminal Ready (DTR)

Does this mean I need a custom cable? Is DTR the same as CTS/RTS? I have spend a lot of effort avoiding serial ports and the problems they incur. Ha!

Thanks for any advice.

Kurt
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Re: Printer Question

Postby AltairClone » January 30th, 2018, 9:16 pm

The Altair 88-2SIO uses the CTS input on the 6850 ACIA (UART) to throttle transmit output. The Altair Clone duplicates this behavior. CTS into a DCE device (as the Altair Clone is wired) is on pin 4 (RTS).

Your printer most likely uses DTR as its handshake output, so yes, a custom cable that connects printer pin 20 to Altair pin 4 is necessary.

Mike
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Re: Printer Question

Postby toml_12953 » January 30th, 2018, 9:19 pm

kurthamm wrote:This is probably a very simple question, but I always have trouble with printers and flow control. I tried to print a banner on my new printer, but I got a buffer overflow error.

The Altair Clone docs identify this serial pin configuration:
Pin Signal
2 XMT from Terminal (out) to Clone (in)
3 RCV to Terminal (in) from Clone (out)
4 RTS from Terminal (out) to Clone (CTS in)
5CTS to Terminal (in) from Clone (RTS out)
7 Signal Ground

My printer docs identify this serial pin configuration:
1 Chassis Ground
2 Serial Data Out - Asynchronous output data line
3 Serial Data In - Asynchronous input data line
7 Signal Ground
11 and 20 Data Terminal Ready (DTR)

Does this mean I need a custom cable? Is DTR the same as CTS/RTS? I have spend a lot of effort avoiding serial ports and the problems they incur. Ha!

Thanks for any advice.

Kurt


No, DTR is not the same as CTS/RTS. Here's a website that shows the signals with a little explanation

http://www.machine-information-systems.com/RS232_Pinouts.html
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Re: Printer Question

Postby kurthamm » February 2nd, 2018, 3:58 pm

Yea, i got my breakout box and tried some combinations of 4,5 and 11,20. Nothing seemed to work and just kept getting buffer overflows on long printouts.

I have a different printer coming that uses CTS/RTS, so that should work for longer prints. This printer works fine unless I try to print a banner.

Thanks for the responses.

Kurt
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Joined: January 18th, 2018, 10:59 am

Re: Printer Question

Postby kurthamm » February 2nd, 2018, 5:15 pm

OK, so this was still bothering me. These are, after all, just electrical signals. I remembered that the printer listed 11 AND 20 as DTR. So, I hooked 4 to 11 and tried again. SUCCESS!

Well, that is resolved. Now to find another puzzle.

Kurt
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Re: Printer Question

Postby AltairClone » February 3rd, 2018, 9:00 am

Success after a day or two of head scratching always feels good!

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