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Crate Remote Control

CAN-control scheme

Monitoring and remote control for NIM, CAMAC, VME and VXI crates


Introduction to the CAN-Bus

The Controller Area Network (CAN) defined by Bosch in 1985 is an advanced serial multimaster communication protocoll. Due to the reliability and technical capability as well as to the available low-price system components CAN is well suited for application in fieldbus system. The most important features of CAN are:

  • in principle unlimited number of nodes (depending on physical layer)
  • serial, asynchronous, object-oriented, multi - master communication
  • 2032 priorities (message IDs) in standard frame
  • max. 8 data bytes per message
  • CSMA(CA (collosion avoidance) bus access priority controlled (ID) with non-destructive bit-wise arbitration
  • wide range of transmission rates, high speed up to 1.6Mbit/s (577kbit/s information)
  • realtime capability, guaranteed latency time for high priority messages <134µs (1Mbit/s)
  • high level of reliability and safety due to integrated error detection (HD=6), handling and confinement, less than 10-13 undetected errors per message
  • twisted pair cabling, line or star topology
  • maximum distances and rates:
    Max. Distance Bit Rate
    40 m 1.0 Mbit/s
    130 m 500 kbit/s
    270 m 250 kit/s
    530 m 125 kbit/s
    ... ...
    10.000 m 5kbit/s

Crate remote Control via CAN-bus


Based on the WIENER µ-processor controlled intelligent fan-tray-units equipped with the WIENER CAN bus interface this remote control can be integrated within an CAN fieldbus system. Up to 126 crates can be controlled within a network. In addition to the remote on/off and SYSRES (VME) the user can control and program remotely every crate parameter via the interface as (* in progress):
  • Crate Identification
  • All voltages and currents
  • Over- undervoltage trip off points (*)
  • Current limit adjustment to lower levels as 100% for module test procedures (*)
  • Temperature measurements: a) Power supply, b) Fan tray air inlet c) air outlet temperature on top of slot 1 (optionally), additional sensors are available for the 6000 crate series
  • All status signals
  • Average speed and induvidual speed of every single fan
  • Configuration and adjustment (*)
The communication between crates and host computer is based on a new intelligent bus protocol (CMS-CAL compatible) characterized by functions like:
  • automatic error message generation (highest priority)
  • minimum level of required bus activities
  • broadcast and group functions
  • task dependent priorities, equal rights for all crates

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This page was created by W-IE-NE-R, A&K.Ruben - 9/98