> Sorry to pick nits, but a (modem) cable that connects HSKo to DTR only is
> simply not going to give you hardware flow control for incoming data with
> any real-world modem. The modem will then either ignore what you feed it on
> pin 20, or it will control the line state depending on pin 20 -- which is
> DTR semantics.
>
> You won't get hardware flow control until you bridge the modem's DTR and
> RTS (or wire RTS only), *and* tell the modem to ignore what happens on pin
> 20/DTR. At that moment, you give up line control and use HSKo with RTS
> semantics.
>
> Repeat: To use the Mac's HSKo for controlling the flow of incoming data
> (RTS), you need to explicitly *remove* DTR semantics both on the Mac side
> (serial driver) *and* on the modem side (AT&D0 and change wiring).
>
> No DTR left on both sides, sorry. Thus, no point in calling the mode
> "cdtrcts".

As far as I understand, flow control between DTR/CTS(Mac side) and
RTS/CTS(other side) works, if HSKo is wired to the other side RTS
with cdtrcts( ,and if cdtrcts means it works as DTR/CTS flow
control ).
Mac think it's DTR/CTS handshaking, and the other side it's
RTS/CTS.
Actually I never expect the other side speaks DTR/CTS flow control
unless it's another Mac or NeXT.

-- kaz-k