CM11A Reliablity issues

Source: Dave Houston, posted to Usenet newsgroup comp.home.automation
on 3 Dec 1999 and reproduced here with permission.

There are four types of lockups. Two can be easily induced, another is
fairly easy to induce, and one is fairly infrequent but is the hardest
to cure.

1. This one can be induced by using another transmitter to send an old
style extended code without any following extended data. This will lock
up all CM11As 100% of the time. It can be cleared by using the other
transmitter to put any command on the power line.

2. This one occurs when an older CM11A (older than about 24 months -
with firmware 7 as returned by the Status request detailed in the CM11A
protocol documentation) and a two-way module such as the LM14A are
powered up simultaneously (e.g. after a power outage). This also will
lock up the older CM11As 100% of the time. It can also be cleared by
using another transmitter to put any command on the power line.

3. A third type occurs when the RS-232 cable is disconnected from the
PC but not from the CM11A. This frequently, but not always, causes
lockups and other weird behaviors. The lockups can usually be cleared
in the same manner as above. This is probably the most frequent cause
but it was the last to be identified and documented.

4. A fourth type is fairly infrequent and seems to be related to a
dangling RS-232 cable and/or brownouts. It cannot be cleared in any
manner other than removing the CM11A from the power line, removing the
batteries and waiting a lengthy period. In most case 45 minutes is
adequate but, in some cases, it takes longer.

All are totally independent of the software used. None have ever been
acknowledged by X-10 but we've come to expect silence from X-10.