Sun HW flow control request

[Mark Reynolds]

<>

	I am trying to find out some information on the zs ( serial ) driver
on the Sun 2.  What I want to do is very simple:  I would like to use a tty
port as an I/O port to a device that obeys hardware flow control. 

	The device would be the DCE ( modem ) and the Sun's tty port would be
the DTE ( terminal ).   If some combination of CTS DSR and CD were made
logically false the DTE ( the Sun ) would shut up and cease to send;  if some
combination of DTR and RTS were made false the DCE would shut up and cease to
send.  From the Sun's point of view these telling the DCE to shut up would
be conditioned on the zs silo being full and/or inability of the software to
eat characters as fast as they are coming in.

	The goal is that the device is uncontrollably shipping completely 
arbitrary bytes at 9600 baud ( but never more than 8K ).  I want to prevent
any lost bytes.  I am sure this has been discussed before.

	I do not have source, nor do I have a hardware manual for the zs.
What I think I have learned so far from poking around in various places is:

	1)  There are an extremely large number of ioctls that may or may
	    not apply to ttys in <sys/ioctl.h>.  Some do obvious and verifiable
	    things ( TIOCCDTR and TIOCSDTR for example ), others are obscure.
	    Most do not seem to be documented in any documentation I have.

	2)  Poking around the zs includes in /sys/sundev would seem to indicate
	    that the zs device has a mode in which it uses hardware flow
	    control ( ZSWR3_AUTO_CD_CTS bit );

	3)  Looking at the terminal line during both inbound and outbound
	    transfers shows that only TxD, RxD, and DTR are active.

My question is, can a tty device be put in a mode which uses hardware
flow control?  If so, how?  If not, what other alternatives are available?
Please help;  this is quite important.

To qualify my question, let me say I am a Sun novice.  I have been around
UNIX for quite a while, and I THINK I understand the RS232 so-called standard.
Please feel free to flame my ignorance and/or stupidity.

Thank you in advance.  Please mail responses to me.  I will summarize if
interest warrants.

Mark Reynolds @ ( Adaptive Optics Associates )

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