Dave,
If by "processor" you mean the sZeries CPC, then your understanding
might be a little off...
My understanding is that the timer just sends timing signals to the CPC,
it is unaware of what the CPC is doing. Basically it is a one way
process. Whether there is a CLO or not, the 9037 never gets the time
from the CPCs. It just sends the time and stepping signals to control
the CPC clock rate. (it also sends offsets for daylight saving/Leap
seconds etc). The only thing the 9037 is aware of is that there is a CPC
connected at the other end of the port. So long as there is a link
established, then it doesn't know what the CPC is doing with the
information. If your CPC is connected to 2 9037 ports, then both 9037
ports send data unaware as to which port is being used by the CPC. The
only thing the 9037 knows about the CPC is how far away it is.
It determines this so that it can "tune" the signal on each port to take
account of time delay etc..
If there isn't a CLO card then you're right in that the clock on the
9037 processor board is used as the time source. However, if you have a
CLO card (which is required when you hook up 2 timers), then I believe
that internally to the 9037 it is the CLO card(s) that are used to
maintain the clock and its steering rate. These use some sort of voltage
controlled oscillator to maintain syncronisation with two timer units
and to enable the clock rate to steer to a corrected time. Whether the
corrected time is a manual input, or from an ETS, I don't think makes
much difference to the CLO - it just steers the clock to the new time.
Regards
Roy
Dave Kopischke wrote:
And my understanding of the function of the timer is to steer the onboard
clocks on the processor. The processor clocks are always the source of time
information. The timer compares the time from the external source to the
time on the processor and either slows the clock down or speeds it up until
they match. If you don't have a CLO card, the timer itself is the time
source (your wristwatch is probably more accurate). You can't get more than
four seconds out of synch or the timer won't be able to generate the proper
steering impulses to get the clocks back in synch. There's lots of detail
in the manuals if you care to attempt to understand it.
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