[Info-vax] Programming the serial port on an Alphaserver 200

[H Vlems]

On 28 feb, 23:18, Steven Schweda <sms.antin... at gmail.com> wrote:
> rtk wrote:
> > It appears that I wasn't clear enough in my first post.
>
>    That's a trend these days.  Actual output from those SHOW
> commands might have been interesting, too.
>
> > fopen(), of course.. what name?  For example, in Unix it
> > would be something along the lines of "/dev/ttyS0", how are the
> > ports accessed in VMS?  Is it just fopen("TTA0:") ?
>
>    Yes, more or less.  "TTA0" is a legit VMS device name.
>
> > SHOW DEVICE _TT reports two serial ports, TTA0: and TTB0: while SHOW
> > TERMINAL on the serial console shows _TTB0:
>
>    I would have expected TTA0 for the console, but it's been a
> while, and I'm too lazy to wake one up right now.
>
> > So, given that TTB0: is the serial console, can I usurp that
> > port and let another program use it?
>
>    It may be possible to "usurp" it, but I'd expect greater
> happiness if you try not to grab a device which is already in
> use.  If the OS does not own the device, then you should be
> able to use it.  Log out (or don't log in) on the serial port,
> connect in some other way, and do a SHOW TERMINAL or a SHOW
> DEVICE /FULL on that device.  If "Owner:" comes up as "No
> Owner", or "Owner process" as '""' ("Owner process ID" =
> "00000000"), then it should be available.  If you want a
> non-privileged user to be able to use it, then you may need to
> set some more than usually permissive device protections.  For
> example (from one of my system start-up procedures):
>
> $ set security /class = device /protection = w:rwlp TTA0:
> $ set security /class = device /protection = w:rwlp TTB0:
>
> "SHOW DEVICE /FULL _TT" should show the current "Dev Prot".
>
>    It might also help to know exactly how you intend to use
> this serial line.  Console terminal only, other gizmo only,
> switched between them, ...
>
> > [...] the serial cable is already threaded [...]
>
>    How many conductors?  If you can live with only the data
> leads, and, I assume, the ground is already common, then five
> conductors would be enough for two lines.  If you ran less than
> eight, then it's your own fault.

On an Alpha Server 1200 device names for serial ports change as a
function of the SRM attribute CONSOLE.
If CONSOLE is set to serial then the two serial ports on the back are
OPA0: (right) and TTA0: (left).
Where right and left are the positions of the ports while looking at
the back of the server.
If CONSOLE is set to graphics then the right serial port is called
TTA0: and the other TTB0:
Hans