UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Orton's rant on serial connection of NIBL computers to modern terminal emulations

TonyDuell · 30th Jun 2020, 4:46 am

That's one reason I have real vintage terminals here, including a DEC VT100 (actually a VT105). Although I am surprised by the number of vintage-ish devices that can't handle 110 baud.

However, strictly RTS/CTS (or DTR/DSR) are not flow control lines. Remember that originally the RS232 interface was used between a terminal and a (dumb) modem. The latter could not do any form of buffering, and therefore there was no flow control between the terminal and the modem. Flow control is between the terminal and the computer/terminal/whatever at the far side of the distant modem. Therefore any flow control has to be able to be transmitted down the telephone line. So Xon/Xoff or whatever. Yes, these signals are commonly _misused_ as flow control lines (I do it myself...) but you can't moan when they don't work.

That said, I'd probably go for the large buffer RAM on the interface PIC solution. It will work with anything, no matter if it correctly handles Xon/Xoff or not. And there are plenty of serial devices that don't (no matter what the documentation says!)

30th Jun 2020, 4:46 am	#5
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Orton's rant on serial connection of NIBL computers to modern terminal emulations That's one reason I have real vintage terminals here, including a DEC VT100 (actually a VT105). Although I am surprised by the number of vintage-ish devices that can't handle 110 baud. However, strictly RTS/CTS (or DTR/DSR) are not flow control lines. Remember that originally the RS232 interface was used between a terminal and a (dumb) modem. The latter could not do any form of buffering, and therefore there was no flow control between the terminal and the modem. Flow control is between the terminal and the computer/terminal/whatever at the far side of the distant modem. Therefore any flow control has to be able to be transmitted down the telephone line. So Xon/Xoff or whatever. Yes, these signals are commonly _misused_ as flow control lines (I do it myself...) but you can't moan when they don't work. That said, I'd probably go for the large buffer RAM on the interface PIC solution. It will work with anything, no matter if it correctly handles Xon/Xoff or not. And there are plenty of serial devices that don't (no matter what the documentation says!)