] I've put (what I think are) the final touches on a new serial driver
] for mac serial ports. This driver uses the machine independant SCC
] driver (shared w/ sun3, sun3x, and mvme68k).

cool.  much thanks for working on this.

] What is different?

] 2) We now properly do flow control. The problem has been that we only have
] one control output from the serial port, and the output's commonly used
] to make the modem hang up the phone (DTR). The new driver adds a new
] flow control mode, cdtrcts, which will use DTR to tell the modem to
] hush. If your RS/232 cable has wired HSKo to RTS, it will work.
] 
] crtscts will watch CTS, and hush when asked. This mode is great for
] printers (like the DeskWriter I have :-), and lets you hang up the
] phone.
] 
] cdtrcts is new, and uses DTR as a handshake output, to get the modem/other
] computer to stop. CTS is still monitored for when we're asked to hush.
] This mode is great for hooking two macs together (with a printer cable)
] or talking to a fast modem. This mode can't make a modem hang up the
] phone (you'd have to send a special AT command).

I think it's great that both these modes will be supported, but
I'm worried about the names.

I think that 'crtscts' should be for where the mac drops HSKo
when it wants the remote device to temporarily stop sending
data.  This is the most common case, and is what the user
wants when s/he is using an "RTS/CTS flow control" modem cable,
which is pretty much the only kind of modem cable made since
modems hit 9600bps.  And, as you say, this is also the behaviour
you want for machine-to-machine serial communications.  I would
add that this is also the proper mode for many serial printers.

The other behaviour, where the mac drops HSKo when it wants
the remote device to hang up or reset, should be the one to
get a new macBSD-only name, IMNSHO, as it will be less often
be the one MacBSD users want.

Something else to consider is if MacBSD should support the GPi
pin.  This "general purpose input" is not supported by most early
macs, but it can be used to detect a modem hang-up on macs that
support it.

comments?

] I tried cdtrcts hooked up to a 386, and, at 57600, was able to get > 10,000
] BYTES/sec throughput (ppp compression was on) w/o a single overrun. :-)

cool again!


--
brian cole, maintainer of the Mac Serial Port Summary:
            http://www.inxpress.net/~bcole/mac/mac_serial_port_summary.txt