RTS/CTS handshaking on a tty

[Stefan Brandle]

In article <50054 at ames.arc.nasa.gov> schoch at trident.arc.nasa.gov (Steve Schoch) writes:
>I have a micro-vax with a DZV (dz0) and a DHV (dhu0) running Ultrix
>3.1.  I would like to use a port on one of these boards with hardware
>flow control (when CTS goes low to the VAX, the VAX should stop sending
>data until CTS goes high again).
I'm not quite whether the CTS stuff works properly for flow control (we use 
XON/XOFF for flow control and CTS/RTS for determining modem/VAX status) but 
system calls do exist to help manipulate this stuff.

>Does Ultrix support such an operation mode for these boards?  If so,
>what is the ioctl I can use to turn it on.
See below.

Example below chopped from a program we concocted locally when we are toggling 
our modem when switching a modem line from outbound to inbound.  We run this 
program as part of a shell script that changes the line status in /etc/ttys to 
`on', does a `kill -HUP 1' and enables dtr on that line.  (We're not using modem
control while calling out -- uucico catches on fast enough when our connection 
dies!) This should give you an idea of where to look.  We are currently using 
this on a machine that's still under Ultrix 2.0, but the 3.0 manual entry looks 
the same so should work.
================================================================================
#include <sys/file.h>
#include <sgtty.h>
/* this only permantly sets modem controls if executed as root - see (4) tty */
...
  file = open(argv[1],O_RDWR+O_NDELAY);
...
  if (ioctl(file,TIOCMODEM,1) != 0) printf("problems in setting modem\n");
  printf("clearing dtr\n");
  if (ioctl(file,TIOCCDTR) != 0) printf ("problems in clearing dtr\n");
  printf("sleeping \n");
  sleep(3);		/* giving the modem time to finish reseting --AT&D3 */
  printf("setting dtr\n");
  if (ioctl(file,TIOCSDTR) != 0) printf("problems in setting dtr\n");
...

Hope this helps,
-stefan
-- 
---------------------------------------------- MA Bell: (708) 260-4110 ---------
Stefan Brandle                  UUCP: ...!{obdient,uunet!tellab5}!wheaton!stefan
Wheaton College			or	stefan at wheaton.UUCP
Wheaton, IL 60187 		"But I never claimed to be sane!"