Concurrent Technologies RCIM, Руководство пользователя

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Appendix C
Calculating RCIM Cable Propagation Delays
This appendix provides calculations to determine if your cable connections introduce
signal delays.
Interconnect Details
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The maximum cable length between each interconnected RCIM boards is 30 meters (~100
feet).
The clock runs at 400ns per tick. If the clock signal takes more than 400ns to make it to
any given slave in the chain, clock skew will occur from that point on. The clock is re-
driven by each pass-through slave.
Due to synchronization and re-drive of the serial data on the cable, each RCIM added to an
RCIM chain adds about 200ns of delay in addition to approximately ~7ns for each meter
of the cable, or ~200ns per 30-meter cable, for a total delay of about 400ns.
Two systems in an RCIM chain with the 30-meter cable will operate within a 400ns clock
tick. Having more than two results in less precise synchronization.
Note that if a pass-through slave system is powered off, the cable clock will not be
propagated to the slaves downstream from it. In this case, the downstream slaves will use
their local oscillator instead of the cable clock.
The user just needs to be aware of the delays associated with each RCIM and cable in a
chain to determine if the level of clock skew is acceptable for the application.