From: Spiro Trikaliotis (ml-cbmhackers_at_trikaliotis.net)
Date: 2008-02-03 10:24:12
Hello,
* On Sat, Feb 02, 2008 at 05:58:52PM +0100 silverdr@inet.com.pl wrote:
> On 2008-02-02, at 17:02, Marko Mäkelä wrote:
> >OPEN doesn't always result in any communication. For example, when
> >no file name is specified on the serial bus, nothing will be sent.
> >Try OPEN1,8,15 with nothing attached to the serial bus. It will
> >succeed.
>
> That's acceptable as long as it is fully deterministic.
It is. At least as far as the IEC bus is concerned, an OPEN without a
filename will result in no activity at all through the bus, but an OPEN
with a filename will result in activity.
> I recall I was urgently needing this many years ago and since after a
> tedious research (there was no Internet at that time) I haven't found
> a reliable solution,
[...]
If you are only handling the IEC bus, you have two options:
1. Try the OPEN with a filename, or
2. send the OPEN without a filename, and send an UNLISTEN (or an UNTALK)
to the specified device afterwards. (The drive will process but
ignore an UNLISTEN or UNTALK if it is not in the LISTEN or TALK
state). After this, the status should be correct.
Notes:
a. This is the behaviour of the 154x and 157x. I have not checked the
1581 or any printer, which might behave differently if there is an
UNLISTEN/UNTALK without being in the correspondig state.
b. While we are at it: The 154x/157x will handle the UNLISTEN and UNTALK
in exactly the same way. That is, an UNLISTEN is also an UNTALK, and
vice versa.
Regards,
Spiro.
--
Spiro R. Trikaliotis http://opencbm.sf.net/
http://www.trikaliotis.net/ http://www.viceteam.org/
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