rts/cts on 3b2 tty ports

[Larry Schroeder]

> Now, what I need is some way to control and query the lines.  Unfortunately,
> AT&T did not distribute the source code the the tty device driver, nor any
> documentation on the tty hardware.  Can anyone give me any information on this?

Assuming the tty ports in question are those of the 3B2 "ports" card, the
tty ports are controlled by the ppc driver and standard Sys V tty line
discipline through the Ports board firmware.  Standard Sys V tty control
flags and requests do not specify any features for access to RTS and CTS
for a port.  Therfore as for most UNIX Sys V systems the user can not
specify their control, the 3B2 "Ports" firmware and driver Does Not provide
any user accessable control for RTS and CTS (May be a problem to your U-B
controller !?).

> On a side note, in /usr/include/sys/termio.h, in the #define's for the
> c_cflag field in the termio structure, there are two undocumented flags:
> RCV1EN and XMT1EN.  Anyone know what these do?  Are they related to the above?

These two cflags in termio.h define setup for an AT&T tty interface to
Teletype's SSI protocol terminals. (This interface is not used on a AT&T 3B2
at this time, but is shown in standard termio.h for most AT&T 3B computers)

The SSI ("standard synch. interface") protocol provides a synchronous
communication frame which may  contain one or two bytes of data or control
characters. The RCV1EN flag identifies when set one-byte per frame on receive 
(two bytes per frame if not set).  XMT1EN is similar for transmit...


			Larry Schroeder
AT&T Information Systems -- Network Architecture Department