CAN-bus interface for remote monitoring and control

The Controller Area Network (CAN) defined by Bosch in 1985 is an advanced serial multimaster communication protocol. 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 ID's) in standard frame
• max. 8 data bytes per message
• CSMA(CA (collision 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)
• real-time 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 can be between 1Mbit/s for 40m up to 5kbit/s for 10,000m.

Crate remote control

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 individual 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