Transcription
MS/TP Communications Bus TechnicalBulletinBuilding Technologies & 1034
2MS/TP Communications Bus Technical Bulletin
ContentsContentsDocument Introduction. 5Summary of Changes. 5MS/TP Bus Overview. 5FC Bus. 6SA Bus. 7Remote Field Bus. 7BACnet Router Configuration. 10Supervisory Engine Configuration for Adding Remote Field Bus. 13BACnet Router Wiring. 14Remote Field Bus Restrictions. 15Remote Field Bus Status and Statistics Attributes. 16Remote Field Bus Status Commands. 17End-of-Line Termination on the MS/TP Bus. 17Baud Rates on the MS/TP Bus. 18Device Addressing on the MS/TP Bus. 19Setting a Device Address. 20Rotary switch dials. 22Enabling Equipment Controllers for Wireless Operation. 23Local FC Bus Rules and Specifications. 23End-of-Line Termination on Local FC Bus. 26EOL Terminator Module. 28TEC26xx and TEC30xx Series Thermostats and Third-Party MS/TP Devices. 29SA Bus Rules and Specifications. 30SA Bus Device Limits. 30Number of NS Series Devices Supported on the SA Bus. 31End-of-Line Termination on SA Bus. 32SA Buses with Multiple Network Sensors. 33Remote Field Bus Rules and Specifications. 34EOL Termination on the Remote Field Bus. 36EOL Terminator Module for Remote Field Bus. 38MS/TP Bus Cable Recommendations. 38Screw Terminal Blocks for Connecting FC and SA Bus Cables. 40Grounding the MS/TP Bus Cable Shield. 41RJ-Style Modular Jack and Cables for SA Bus. 42Commissioning Devices on the MS/TP FC Bus. 43Peer-to-Peer Communication. 43Related Documentation. 43Appendix: FC Bus Auxiliary Devices. 46Repeaters. 46Configuring Repeaters. 46MS/TP Communications Bus Technical Bulletin3
Fiber-Optic Modems. 48Routing and Connecting the Fiber Cables. 48Connecting Modems to MS/TP Bus. 48Fiber Modem between Two Segments. 48Setting Termination on Fiber Modems. 49Surge Protectors. 50Appendix: Maximizing and Troubleshooting MS/TP Bus. 54Maximizing Tips. 54MS/TP Bus Health Factors of the Diagnostics Tab. 55Bus Health Index. 56Bus Performance Index. 56Statistics Attributes. 57Analyze Field Bus Command. 58Parameters That Affect MS/TP Communication. 60Duplicate Addresses. 61Common Problems. 61Correcting Physical Bus Problems. 63Correcting Bus Overload Problems. 63Reading the Baud Rate of Devices. 64Counting the COVs. 65Disabling a Device on the Bus. 65Automatic Low Resources Monitoring. 65The Object Engine Input Queue. 65Available Free Memory. 66Protocol Engine Input Queue. 66Protocol Engine Output Pending Queue. 66Appendix: Optimizing SA Bus Traffic. 67Excessive Traffic. 67Inputs and COVs. 67Outputs and Commands. 69SA Bus Traffic Reduction. 70Product warranty. 71Patents. 71Software terms. 71Contact information. 714MS/TP Communications Bus Technical Bulletin
Document IntroductionThe BACnet protocol MS/TP communications bus is a local network that connects supervisorycontrollers and equipment controllers to field point interfaces.This document describes the specifications, device limits, and rules of the MS/TP communicationsbus, as well as how to wire and terminate devices, and troubleshoot device communication onthe MS/TP bus. The remote MS/TP field bus is also described. With the addition of a BACnet IP toBACnet MS/TP Router, the Remote Field Bus allows connection to remote equipment controllersover IP.This document is intended for the user who needs to know the rules, requirements, limits,specifications, and configuration of the MS/TP bus to design, wire, or troubleshoot an MS/TPapplication.Summary of ChangesThe following information is new or revised: Updated Related Documentation table to include the latest SNE and SNC engines, and theOpen Application Server (OAS). Document updated to include the new XMP I/O expnsion modules Document updated to include the new WRG1830/ZFR183x Pro Wireless Field Bus SystemMS/TP Bus OverviewThe BACnet protocol MS/TP communications bus is a local network that connects supervisorycontrollers and equipment controllers to field point interfaces. The bus is based on BACnetstandard protocol ANSI/ASHRAE Standard 135.The BACnet MS/TP protocol is a peer-to-peer, multiple master protocol based on token passing.Only master devices can receive the token, and only the device holding the token is allowed tooriginate a message on the bus. The token is passed from master device to master device usinga small message. The token is passed in consecutive order starting with the lowest address.Subordinate devices on the bus only communicate on the bus when responding to a data requestfrom a master device.Important: Do not connect MS/TP devices and N2 devices to the same bus. MS/TPcommunications buses follow different protocol and wiring rules from N2 communicationsbuses, and MS/TP devices and N2 devices are not compatible on the same bus.An MS/TP bus is used for two types of buses: a Field Controller bus (FC) and a Sensor Actuator (SA)bus (Figure 1). The MS/TP bus can also be extended remotely over the IP network with the additionof a BACnet IP to MS/TP router.The FC bus, SA bus, and Remote Field Bus are networks of daisy-chained devices. Each bus hasonly one bus supervisor, depending on which controllers are connected. On a local FC bus, the bussupervisor is the supervisory engine. On the local SA bus, the bus supervisor is a field controller. Onthe Remote Field Bus, the bus supervisor is the BACnet IP to BACnet MS/TP Router (hereafter calledthe BACnet Router), which works with the supervisory engine when a Remote Field Bus is installed.MS/TP Communications Bus Technical Bulletin5
Note: When you install a BACnet Router for adding a Remote Field Bus to the job site, youneed a site-level, unique MS/TP network number and device object ID (if it contains a deviceobject) for the BACnet Router. In addition, it is critical that you determine if a BACnet BroadcastManagement Device (BBMD) is required for the BACnet Router. If you configure the BACnetRouter as a BBMD, assign a static IP address to both the router and the NxM or ODS where youare configuring the MS/TP bus. For an existing installation, contact the BAS Manager, BuildingManager, or IT department for information on available network numbers, device object IDs,and existing BBMDs for crossing IP subnets. Information on configuring a BBMD in a BACnetRouter (if it supports them internally) is available from the router vendor.The bus supervisor communicates with devices on the supervised bus and with devices on the next(higher level) bus on the network. The bus supervisor typically starts the communication on theFC bus, remote FC bus, or SA bus. If an SA bus, FC bus, or Remote Field Bus does not have a bussupervisor, the master device with the lowest device address value on the bus and a specific baudrate selected starts the communication.The WRG1830/ZFR183x Series Wireless Field Bus System enables wireless communication onan MS/TP bus, allowing you to create wireless connections between Metasys General PurposeApplication Controllers (CGMs), VAV Box Controllers (CVMs), Advanced Application Field EquipmentControllers (FACs), Field Equipment Controllers (FECs), or VAV Modular Assemblies (VMAs), Input/Output Modules (IOMs) Expansion Modules (XPMs), and Network Automation Engines (NAEs),Network Control Engines (NCEs), SNCs, and SNEs.See Enabling Equipment Controllers for Wireless Operation and Related Documentation for detailedinformation about the WRG1830/ZFR183x Series Wireless Field Bus System.Note: The ZFR1800 Series Wireless Field Bus System is not supported on the Remote Field Bus.FC BusAn FC bus connects a Metasys system NAE, NCE, SNC, or SNE to CGMs, CVMs, FACs, FECs, VMAs,IOMs and XPMs. Third-party BACnet MS/TP devices such as the TEC26xx and TEC30xx seriesthermostats can also be connected to the FC bus.6MS/TP Communications Bus Technical Bulletin
Figure 1: Example of an MS/TP Communications BusOn an FC bus, the NAE, NCE, SNE, and SNC is the bus supervisor. An FC bus supports up to threebus segments that are connected with network repeaters (Figure 10). See Local FC Bus Rules andSpecifications for more information.SA BusThe SA bus connects NCEs, SNCs, CGMs, CVMs, FACs, FECs, and VMAs (equipment controllers)to endpoint devices, such as IOMs, XPMs, network thermostats, network sensors, and JohnsonControls Variable Speed Drives (VSDs).On an SA bus, an NCE, SNC, CGM, CVM, FAC, FEC, or VMA is the bus supervisor. The SA bus isa private MS/TP bus that only supports those devices that can be defined using the ControllerConfiguration Tool (CCT) programming tool. The bus does not support bus segments (Figure 14).See SA Bus Rules and Specifications for more information.Remote Field BusThe Remote Field Bus uses a BACnet Router to connect remote BACnet MS/TP devices to theMetasys network. These devices include CGM, CVM, FACs, FECs, and VMAs controllers, the IOMsand XPM expansion modules, the TEC26xx and TEC30xx Series thermostats, and other BACnetMS/TP field devices. Although several routers from different manufacturers are available, therecommended device is the LIP-ME201 BACnet Router from Loytec Electronics GmbH. Do not useany USB-powered MS/TP to IP converter, including the Johnson Controls BACnet to MS/TP Router(TL-BRTRP-0).Use a Remote Field Bus for applications where routing an RS-485 network directly to a supervisoryengine is not practical because of distance, cost, or poor accessibility. In many cases, an IP networkMS/TP Communications Bus Technical Bulletin7
connection is available at both the supervisory engine and at some point near the BACnet MS/TPdevices. By leveraging the Metasys Remote Field Bus capability with installing the BACnet Routernear the BACnet MS/TP devices, you can reduce system cost. Also, when you choose MS/TP deviceintegration with a router rather than BACnet Integration, access to proprietary attributes, messagetypes, and objects from Metasys equipment controllers is available. This functionality providesyou with more information and more capability than the standard BACnet attributes, services,and object types. For example, at the Site Management Portal you can view proprietary attributessuch as communication statistics from mapped Metasys equipment controllers. Also, remoteMS/TP device integration supports the CCT Passthrough option for downloading devices directlyconnected to the Remote Field Bus (but not to devices connected to the sensor bus).Figure 2 shows an example of a Metasys network with a Remote Field Bus.Figure 2: Example of a Remote Field BusThe Remote Field Bus is defined at a Metasys supervisory engine or OAS Workstation (Figure 3)through field bus integration, similar to how a local MS/TP field bus is added. The Remote Field Busappears on the All Items Navigation tree in the Site Management Portal UI. You can also provide acustom name to clearly identify the type of integration.8MS/TP Communications Bus Technical Bulletin
Note: To ensure acceptable system performance, make sure that you map all devices andobjects that originate from a Remote Field Bus to a single supervisory engine, for example,if you have two SNEs (SNE-1 and SNE-2), each with a separate Remote Field Bus. Device 1 isdefined under SNE-1, and Device 2 is defined under SNE-2. In this arrangement, make sure youdo not map Device 1 to SNE-2 or map Device 2 to SNE-1. If you mix remote field device mappingbetween supervisory engines, the Metasys system may start very slowly, and devices may havedifficulty staying online.Figure 3: Example of a Remote Field Bus with OASApplications for the Remote Field Bus include: Any intra-building, inter-building, or remote location that has IP network connections readilyavailable Locations where it is cost prohibitive or difficult to run MS/TP wiring between devices and thesupervisory engine, due to distance, cost, accessibility, or customer factors Locations where equipment controllers are segregated from the supervisory engine Intra-building applications that connect segregated locations within a building (for example,connecting penthouses to mechanical rooms) Remote buildings where an MS/TP bus is not already available, but an Ethernet BACnet/IPnetwork is (for example, university or hospital campuses) Sites with a reliable network between buildings that do not need to have a separate SNE orNAE for the building (for example, school districts)MS/TP Communications Bus Technical Bulletin9
Note: The ZFR1800 Series Wireless Field Bus System is not supported on the Remote Field Bus.For details on how to add a Remote Field bus, refer to the MS/TP Field Bus Integration Object sectionin Metasys SMP Help (LIT-1201793). For details about how to add a Remote Field Bus to a Metasyssupervisory engine with an ODS, refer to the ODS Commissioning Guide (LIT-12011944).Additional background on the Remote Field Bus is covered in the following sections: BACnet Router Configuration Supervisory Engine Configuration for Adding Remote Field Bus BACnet Router Wiring Remote Field Bus Restrictions Remote Field Bus Status and Statistics Attributes Remote Field Bus Status CommandsBACnet Router ConfigurationConfiguration of the BACnet Router varies by vendor and model of the device, but severalimportant configuration settings are required for all routers. Table 1 lists those settings and Figure4 provides an example. For more details on BACnet Router parameters, refer to the documentationprovided with your router.Note: When you install a BACnet Router for adding a Remote Field Bus to the job site, youneed a site-level, unique MS/TP network number and device object ID (if it contains a deviceobject) for the BACnet Router. In addition, it is critical that you determine if a BACnet BroadcastManagement Device (BBMD) is required for the BACnet Router. If you configure the BACnetRouter as a BBMD, assign a static IP address to both the router and the SNE or NxE or ODSwhere you are configuring the MS/TP bus. For an existing installation, contact the BAS Manager,Building Manager, or IT department for information on available network numbers, deviceobject IDs, and existing BBMDs for crossing IP subnets. Information on configuring a BBMD in aBACnet Router (if it supports them internally) is available from the router vendor.10MS/TP Communications Bus Technical Bulletin
Table 1: BACnet Router AttributesBACnet Router AttributeDescriptionNameNetwork Number (forEthernet BACnet/IP)A unique identifier defined for the BACnetIP network connection on the BACnetRouter. The supervisory engine uses thisnumber to locate the device.Network Number (forBACnet MS/TP, Port 1)A unique identifier defined for the BACnetMS/TP network connection on the BACnetRouter.Device IDThe Device ID is the instance number forthe BACnet Router. This number must beunique across the building networks for alldevice instances.Device NameBACnet/IP BroadcastManagement Device(BBMD)MS/TP MAC AddressBaud RateMS/TP Max MasterA name to identify the BACnet Router. Thisname must be unique across the buildingnetwork.The IP network subnets used by boththe BACnet Router and the supervisoryengine normally require that you defineBBMDs on each subnet if those IP subnetsare different. Each IP subnet generallyrequires exactly one defined BBMD. Manyrouters include BBMD capability in order tosimplify this requirement.The MS/TP MAC address of the BACnetRouter you select must not conflictwith any other MS/TP device on thesame wire. Address zero (0) is generallyrecommended. For other field devicesconnected to the same RS-485 MS/TPbus, use sequential addressing followingthe Metasys MS/TP bus addressingrecommendations and reserved addresses.No single MS/TP MAC address can be usedby more than one device on the same MS/TP bus regardless of the type of device.The RS-485 connection on the BACnetRouter requires a specified baud ratein order to initiate communication withfield devices that may use auto-baud rateconfiguration.The highest master MS/TP node numberused on the bus.MS/TP Communications Bus Technical BulletinUser Action or Recommended SettingSpecify the network number assigned for BACnet/IP connections to the BACnet network. Do notuse 2000 or 65000 as the network number; thesenumbers are used for existing embedded networks.Note: In most cases, the IP side of the BACnetRouter shares the same Network Number asall of the BACnet IP connections in one BACnetnetwork (example: 1001). Figure 4 shows anexample.Specify the network number for the BACnet Routeron the MS/TP side with the network addressspecified in the Metasys supervisory engine underwhich the Remote Field Bus is defined. The MS/TPside of each BACnet Router must have a uniqueNetwork Number for the site because each remotebus is a separate network (example: 2801, 2802,2803). Do not use the same network number as anyof the SNE or NAE MS/TP trunks. Figure 4 shows anexample.Specify a unique number.Note: As you add routers, be sure to replacethe router's default device ID with a uniquevalue for your site. The router's device IDmust be different from the device ID of allother BACnet devices at the site.Specify a unique name.Enable and configure the router BBMDs with anappropriate broadcast distribution table.default 03840012711
Table 1: BACnet Router AttributesBACnet Router AttributeDescriptionUser Action or Recommended SettingNameThe Max Info Frames setting on the BACnetRouter you specify should be high enough 80 to 100 (all devices are Johnson Controls fielddevices)to allow the transmission of at least asMS/TP Max Info Framesmany MS/TP frame packets as there areoravailable MS/TP frame buffers in the20 (some or all devices are third-party field devices)router.The maximum size of a BACnet APDU(Application Layer Protocol Data Unit)480accepted by the device. For most BACnetMax APDU LengthRouters, this is a read-only attribute that(or use default)is fixed to the maximum value defined forBACnet MS/TP.Router ConfigurationA password that you must enter to access To protect from intruders, change the defaultPassword (if available)the BACnet Router configuration settings. password.The BACnet Router requires common IPcommunication configuration settings forIP settingsSet these appropriately for the site and the router.the UDP port (default 47808), IP network,and IP subnet mask.Figure 4: Setting Network Address or Network Number12MS/TP Communications Bus Technical Bulletin
For BACnet/IP configuration you need to match the network number specified on the IP side ofthe BACnet Router with the network address specified in the device object of the engine of theOAS. See Figure 4.For BACnet MS/TP configuration match the network number specified on the MS/TP side of theBACnet Router with the network address specified under the Hardware tab of the Remote FieldBus Integration. The network address must be unique for each remote field bus at the site. SeeFigure 4.Supervisory Engine Configuration for Adding Remote Field BusYou define the Remote Field Bus at a Metasys supervisory engine much like you define a local fieldbus. Important settings include Trunk Number and Network Address.Trunk NumberOn a supervisory engine, trunk numbers 1 and 2 are reserved for the local field bus integration.Trunk numbers 3 to 20 are reserved for Remote Field Bus integrations. The quantity of field busessupported on any particular device varies according to the specific device in use. Generally, thenumber of supported trunks is less than the maximum trunk number allowed (Table 2). Forexample, an OAS supports 16 field buses maximum, not 20 field buses as the trunk number rangeMS/TP Communications Bus Technical Bulletin13
would suggest. If the specific device does not support a local field bus, start with trunk 3, as trunknumbers 1 and 2 are not supported.Network AddressThe network address you specify for a Remote Field Bus integration must match the BACnet RouterMS/TP-side network number you specify. The network address must be unique at the site. Keep inmind that each MS/TP trunk on each SNE has a network number that needs to be considered whendetermining a unique ID. This address is used to locate and establish communication between theRemote Field Bus and the router. A defined Remote Field Bus can only work with one router. If youneed to change the network address of a Remote Field Bus after it has been configured, you mustrestart the Metasys supervisory engine to complete the re-configuration.Number Of Field Buses AllowedThe total number of local and remote field buses allowed depends on the type of controller asoutlined in Table 2. For example, an NIE55 can have up to eight field buses, but an NCE25 or NIE29can only support one local field bus and no remote field bus.Table 2: Maximum Number of Field Buses per ControllerControllerNAE55 / NIE59NAE35 / NAE45 / NIE39 / NIE49NCE25 / NIE29NAE85 / NIE89ODSOASSNC25150x-0x / SNC2515x-04x / SNC1612x-0x /SNC1612x-04xSNE22000-0SNE110L0-0SNE10500-0 / SNE11000-0Maximum Number of Field Buses (local and remote)841 (local field bus only; Remote Field Bus not supported)1616163604Note: The Remote Field Bus supports up to 32 field devices per BACnet Router on a buswith all Johnson Controls devices, or up to 16 field devices on a bus with a mix of JohnsonControls and third-party devices. Limitations are listed in the Metasys System Configuration Guide(LIT-12011832). Also, to take advantage of bus diagnostics, at least one Johnson Controls fielddevice is required on the Remote Field Bus.Configuration Attributes Only For Local Field BusIf the same field bus configuration attribute is specified at both the BACnet Router and the RemoteField Bus, the attribute setting on the BACnet Router prevails. For example, if a Baud Rate of 38400is specified at the BACnet Router but a Baud Rate of 76800 is specified on the Remote Field Bus,38400 is used as the Baud Rate on the bus. To be consistent, we recommend that you match theRemote Field Bus attribute values with that of the router, or you can keep the default values at theMetasys supervisory engine. See BACnet Router Configuration for
bus (Figure 1). The MS/TP bus can also be extended remotely over the IP network with the addition of a BACnet IP to MS/TP router. The FC bus, SA bus, and Remote Field Bus are networks of daisy-chained devices. Each bus has only one bus supervisor, depending on which controllers are connected. On a local FC bus, the bus
