Specifications

Figure 25: MS/TP Object Diagnostic Tab
Bus Health Index
The Bus Health Index is a snapshot of the immediate number of errors on the bus. This index provides a weighted
moving average of four MS/TP bus error counters: Framing Errors, Header CRC Errors, Data CRC Errors, and
Lost Tokens. The ideal value for the Bus Health Index is zero.
Because the average is reevaluated every 30 seconds, the average gradually returns to zero if no new errors occur.
As such, if errors occur only periodically (for example, only when a source of bus interference [such as a welder] is
in use), the Bus Health Index may return to zero before you see the value indicate that there are errors. If you suspect
that errors are occurring, look at the four error counter attributes. Alternatively, you can trend the Bus Health Index
to see when or if it changes during the course of the day.
The Weighted Bus Health Constant attribute is an adjustment factor that determines how quickly the Bus Health
Index returns to zero if there are no new errors. The smaller the value of the constant, the slower the index returns
to zero.
Typically, the errors indicated by the Bus Health Index are physical bus problems. See Correcting Physical Bus
Problems.
48MS/TP Communications Bus Technical Bulletin: Appendix: Maximizing and Troubleshooting the MS/TP Bus