Common problems - Metasys - LIT-12011034 - General System Information - Metasys System - Release 11.0

MS/TP Communications Bus Technical Bulletin
Product
Building Automation Systems > Building Automation Systems > Metasys System
Document type
Technical Bulletin
Document number
LIT-12011034
Version
Release 11.0
Revision date
2022-02-07

Several factors can influence the behavior of the MS/TP bus. In addition, certain problems can affect the bus in multiple ways and have more than one symptom, making the exact diagnosis difficult. For example, duplicate addresses on the bus can degrade performance, make a device go offline, or stop communication completely. Table 1 lists common problems that you should consider when troubleshooting an MS/TP bus. The first row, Multiple Symptoms, lists possible problem causes that can have multiple symptoms.

Table 1. Common problems

Symptom

Possible causes

Multiple symptoms

  • Excessive bus errors are occurring.
  • A device was added or changed with a duplicate address (may not be the same address as some devices having problems, and may have happened some time before the problem was noticed).
  • Wiring errors or wire problems exist.
  • The baud rate was changed on some devices on the network, but not all devices.
  • Max Manager was changed incorrectly (this may have happened some time before the problem was noticed).
  • A download is in progress.
  • There is a fault at a device.
  • A repeater is needed or configured incorrectly.
  • There is a duplicated Device Object name or instance.
  • The EOL termination is improperly set.
  • The BACnet Router used with a Remote Field Bus is defective or has poor performance.
  • The same Network Number is being used on the MS/TP side of more than one BACnet Router, NAE, SNE, or third-party gateway at the site.

Poor performance

  • Excessive bus traffic exists (bus overload).
  • Baud rate may be set too low.
  • Too many devices may exist on the network.
  • Unaccounted devices are on the network (that is, not mapped to the NAE or SNE ).
  • Unusually slow devices are on the network or devices that are slow to pass the token.
  • Multiple integrations (Remote Field Bus integration or BACnet integration) are using the same BACnet Router.
  • More than one supervisory device is using the same BACnet Router.

Devices go offline

  • Device is failing to respond to the NAE's or SNE's request.
  • Power or other failure occurred at the device.
  • Communication is disabled at the device.
  • Multiple integrations (Remote Field Bus integration or BACnet integration) are using the same BACnet Router.
  • More than one supervisory device is using the same BACnet Router.

Device does not come online

  • The device may be connected to the wrong bus.
  • The baud rate of a new device is incompatible with the baud rate of the running network.
  • No device on the network is configured to use a specific baud rate (normally the network engine ), but all devices are set to use auto baud. At least one device, typically the bus supervisor ( network engine ), must have an assigned baud rate. Set the baud rate in the bus supervisor and set all other devices to Auto baud.
  • Device failed to download Main Code.

  • The BACnet Router needs a BBMD defined or the BBMD is defined incorrectly.

  • The same Network Number is being used on the MS/TP side of more than one BACnet Router at the site.
  • A BACnet Router has failed or locked up. This problem may occur if you use a router that is neither tested nor recommended.
  • Duplicate addresses exist