IMC CANSAS - Page 126

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126 Operation

DCF77: This mode works like the square mode (also a 1 Hz TTL-level signal). But here, the square-

wave signal conforms to the DCF77 standard. This means that it also contains the time and date

information, which produces a gap in the 59th second of every minute. imc CANSAS has no use for

the time/date information and uses the signal like an ordinary square-wave. imc CANSAS itself

cannot be a DCF-master. For synchronization purposes, it can only play the role of slave.

For all synchronized operating data, a time accuracy of 100µs or better is ensured if the communication

between the master and slaves is working properly. Typically, the offset is even an order of magnitude

smaller, about 10µs.

All imc CANSAS units configured as slaves for synchronization purposes are soon synchronized (after

approx. 2s) upon startup of a master. Internally, they work with a PLL which already begins to operate at

the specified accuracy within a very short time.

Limitations

In case a imc device ( e.g. imc BUSDAQ-2, -X or busLOG) is operated in sleep/resume mode,

synchronization after resume is not possible.

Please note, that different filter settings cause different delays as well.

imc CANSAS as Master: If imc CANSAS is configured as Master for synchronization purposes, note the

following: In the CAN-1 protocol, the Master stops all slaves after booting. Then comes a phase during

which the module flashes yellow and red for 5s (this applies to all operating types) and does not yet

measure. Then measurement starts. If there are slaves, they begin to measure at the same time. The

purpose of this starting procedure is that different imc CANSAS-modules within a system can be activated

simultaneously but need different amounts of time to boot.

imc CANSAS as Slave: After booting, a slave waits for a signal from the master. If there is no master to

send a synchronization signal, the slave doesn't start. Once the master does become active, the slave

starts at the same time. If the master has an outage, the slave continues to work anyway. Of course, if

that happens, it cannot really operate synchronously, but it does continue to measure at the same

quartz-controlled pulse rate which it last had. If during such a situation a master suddenly is activated,

what happened next depends on whether or not the master is (approximately) in the same beat as the

slaves (and, in particular, shares the same phasing). If yes, the slave gradually adapts itself to the master's

phase, which can take a few minutes. If not, the slave is totally re-synchronized. Towards this end,

measurement is briefly interrupted and later re-started. In CAN-1 protocol, the newly-started master

would stop all slaves anyway in order to start them simultaneously afterwards.

Setup:

Select Special function in the tree diagram at left. On the right side, select the index card

Synchronization, in which you set the synchronization type. The default is No synchronization. The

module can be set either as a master or slave for synchronization purposes, as desired. This is also where

to set whether to use the TTL-signal (1s square-wave) or the CAN-1 protocol for synchronizing via the

CAN-Bus.

Other manuals for IMC CANSAS