don@cs.qmc.ac.uk (Don Beal) (08/24/86)
Expires: References: Followup-To: Distribution: Keywords: Help! Does anyone understand the RTS/CTS problems on the Atari well enough to explain the problems below, and hopefully, offer a fix? The Atari TOS has, as one of its options for the RS232 (modem) port, the option to use the RTS/CTS lines. I needed this for my modem because although the ST talks to the modem at 1200/1200, the modem communicates across the telephone line at 1200/75 (a British standard), and hence output from the ST needs to be flow-controlled by the modem which is "speed buffering" and sending at 75 baud. My first attempt with the flow control actually worked (although see next paragraph), but had the extraordinary side effect of heavily corrupting the (non-flow-controlled) incoming data at 1200. Investigation proved this wasn't the modem, but pin 3 on the Atari (receive data) distorting the incoming signal!!!! (Yes, I know this is inconceivable, but it happens.) No distortion if TOS asked not to use flow control, or RTS/CTS is disconnected. Further investigation revealed all sorts of other problems with the flow control. It wasn't working properly at all. Depending on the transmission rate of characters (i.e. gaps between characters versus no gaps), and whether or not simultaneous sending and receiving was in progress it would send 256 characters and then lock up, or send the first character, pretend to send the next 255 then lock up, or work ok. The "ST internals" (abacus) book describes how TOS handles CTS incorrectly and this explains some of the symptoms, but not the incoming data corruption. Is there anyone who knows enough to supply more detail and offer a fix?