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Author Topic: How or When is the CM11A Clock Updated?  (Read 14388 times)


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How or When is the CM11A Clock Updated?
« on: May 29, 2006, 10:40:39 AM »

How or when is the clock updated?  Any time I open the program, I'm in the habit of updating the clock.  Is this a un-needed step?  Does the clock update if the program isn't open for several weeks?

« Last Edit: September 02, 2006, 07:11:49 PM by TakeTheActive »

Charles Sullivan

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Re: CM-11 Clock?
« Reply #1 on: June 02, 2006, 01:19:48 AM »

As long as the CM11A is connected to AC power, the clock's accuracy is controlled from the power line frequency.   Nominally 60 Hz in the USA, this frequency is maintained by the power company so that AC clocks will be accurate on the average, but it can swing back and forth quite a few seconds over the short term as the load on the power company's generators shifts during the course of the day.   Whether or not your frequent updates improve anything depends on: 1. the accuracy of your PC's clock and 2. where you happen to catch the swing of the power line frequency at that moment.

During periods when it's disconnected from AC power, the CM11A clock is maintained by the battery backup and internal circuitry which is not very accurate, typically losing 6-8 minutes per day.  However when AC power has been interrupted, the CM11A detects this and automatically requests a clock update from the PC and the ActiveHome software (and most other CM11A control software) complies with this request as soon as it's started.
Yesterday it worked.
Today it doesn't work.
X10 on Windows is like that.

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Re: CM-11 Clock?
« Reply #2 on: June 07, 2006, 05:53:50 PM »

Whenever the CM11 is unplugged it polls the PC with an "A5" value and refuses to respond until the PC has responded with the appropriate response

If the interface detects that it has suffered a power-down situation, it will ring the PC and poll with a specialized code to indicate that the macros must be refreshed.

5.1.   Power-fail Macro Download Poll Code.

In order to poll the PC, the interface will continually send:

   Poll:      7   6   5   4   3   2   1   0
   Value:     1   0   1   0   0   1   0   1         (0xa5)

This signal will be repeated once every second until the PC responds.

To stop this polling, the PC responds with a hex code of 0xfb and immediately follows with a download to the CM11's memory of the current system time. As previously said, your ActiveHome software should take care of this situation.




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Re: CM-11 Clock?
« Reply #3 on: August 21, 2006, 09:39:25 PM »

Just a reminder:
CM11A does not require battery for operation of the following type:
  A10 on, A10 off Delay 5 minutes
Nice to know as you don't have to worry about them.
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