rts/cts on 3b2 tty ports

[Robert Viduya]

We just got a few 3B2s donated from AT&T and I'm trying to get the tty ports
to talk to an Ungermann-Bass network using hardware flow-control.  The network
implements hardware flow-control using the standard EIA-RS232 lines RTS and CTS
in a non-standard way (the standard allows only one way flow-control; the UB
equipment needs two way flow-control).  Basically, RTS is used to control the
data flow from the network box to the terminal (or 3B2, in this case).  CTS is
used to control data flow from the terminal (3B2) to the network box.  The two
lines are independent of each other (deviating from the RS232 standard).

The 3B2s use an 8-pin modular jack (kinda looks like a phone jack).  Two of
the pins are marked as "Reserved" (pins 2 and 8), but they are wired to the
RTS and CTS lines (pins 4 and 5) on RS232 25-pin connector.

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?

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?

				robert
-- 
Robert Viduya
Georgia Institute of Technology

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