AltairClone.com

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

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

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

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

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

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

Mike