Spec075.pdfHART(Highway Addressable Remote Transdu

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详细说明：HART(Highway Addressable Remote Transducer)，可寻址远程传感器高速通道的开放通信协议，是美国ROSEMOUNT公司于1985年推出的一种用于现场智能仪表和控制室设备之间的通信协议HAR 9390 Research blvd. Ste.1-350 Austin. TX78759 USA Te∴:512-794-0369 COMMUNICATION FOUNDATION FaX:512-794-3904 Addendum to TDMA Data-Link layer Specification(HCF SPEC-075) May17,2008 Since release of the haRT Communication Protocol Revision 7.0 Specifications in September 2007 HCF Staff and Technical Working Groups updating and developing test specifications have closely scrutinized the protocol specifications. Any anomalies, errors or omissions discovered in the Specifications have been identified, tracked and resolved. Changes clarifications and corrections resulting from thc anomalics discovered and resolved during this process are dctailed in this addendum This addendum provides developers with the most current, accurate and up-to-date information on the harT 7 Specifications. Each change is detailed below by subsection and brief explanation of the change. All changes described in this addendum are mandatory. HART-enabled product implementations must comply with the specification corrections and clarifications described in this addendum Subsection 7.2/Table1 In Table I modify the READ MAX BACK OFF EXPONENT ADD CONNECTION and DELETE CONNECTION services as follows READ MAX BACK OFF The maximum value that can be assumed for the back -off EXPONENT exponent used in shared slots. valid values are 14, 5,6,7. Max BackoffExponent defaults to 4. Unsigned-4 Max BackoffExponent △ DD CONNECTION Adds a new connection to a device via a specified grap Unsigned-16 Handle for this connection connectionhandle Unsigned-16 graphId graphld for the connection Unsigned-16 node Nickname address of device being connected via the specified graph DELETE CONNECTION Deletes an existing connection Unsigned-16 Handle of an existing connection connectionhandle Copyright c 2008 HART Communication Foundation Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 Subsection 8.2.4: The Transmit bit in advertise dlPdUs is with respect to the joining devices. In other words, when the link transmit, bit 6, is set the joining devices may use the link to propagate a join request lo the Network Manager:. Consequently, paragraph 3 of subsection 8.2. 4 must be modified to read Once the basic network information is disclosed, the Advertise dlpdu lists all of its join links b superframe. In addition, each link is identified as either transmit or receive from the perspective of thc joining devicc. The joining devicc shall assumc all And the link specification modified as follows For each link Unsigned-16 Join slot. The specific slot within the superframe for this Link Bits Join slot channel offset x.7 Reserved. Must be set to zero. No device shall make any assumption regarding their possible future use of this bit x6Whenset.thelinkisforDLPDUtransmisionbytheioiningdevice. X.5x.0 Channel offset. The frequency channel offset for this slot. This value is used to calculate the link frequency/ channel Subsection 9.2.2 make this more clear in the specificalion t he last two paragraphs in Subsection 9. 2. 2 must be. To The link channel calculation uses an ordered list of monotonically increasing channel numbers modified to read as follows The bit number of the least significant active channel is placed at index zero in the array. The bit number corresponds to the index into the Physical Channel Table for the Physical Layer in use. The Active Channel value is used to index into the active Channelarray Channel= Active ChannelArray[ Active Channel The result is the channel that must be used for communication in that absolute slot number The Active Channel Array is an ordered list beginning with the smallest active channel index(at Active ChannelArray od through the largest Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 Subsection 9.2.3 Details on averaging the rsl must be clarified. After paragraph 4 these details must be inserted as follo The device's ability to communicate with a neighbor is a key metric in forming and grooming the mesh network. Consequently, statistics are maintained in each neighbor table entry. These include timestamp of the last communication with the neighbor ackets transmitted and received and the average Received Signal Level(rsD); statistics on the pa For linked neighbors, RSL is calculated using an IIR filter using the following equation: RSL =RSL-RSL/RSLDamp)+( MeasuredRSL /RSLDamp Where MeasuredRSL is the Rsl for the current packet and RSLDamp is the damping factor. RSLDamp must be a power of 2 and defaults to 64. For discovered or un-linked neighbors (i.e. neighbors the device does not communicate with) the highest RSL value is returned. If a link to that neighbor exists, the LastTime Communicated is used to trigger transmission of Keep Alive packets. a Keep-Alive must be transmitted to the neighbor(see Subsection 9.3)whenever the LastTime Communicated is greater than the keepAliveInterval. Keep-Alive transmissions are repeated until a new dlpdu is received from the neighbor In Table 7 of subsection 9.2.3, BOCntr must be increased in size from 5 bits to 8 bits. The corresponding entry in Table 7 must be modified as follows 「 Unsigned8 BOCntr Back-off countdown in collision avoidance algorithm for shared links Subsection 9. 2.4 The Graph IDfield is overloaded combining frame-based routing, graph-based routing and Invalid"Graph in the same fields. This must be clarified. Consequently, the first paragraph in Subsection 9.2.4 must be modified to read as follows The graph provides the routing information to guide the delivery of a packet to its final destination a graph is a directed list of paths that connect two devices within the nctwork. Both upstream (toward the Gateway)and downstream graphs are used in WirelesshART. The Network Manager is responsible for correctly configuring each graph. Graphs have an ID; a list of neighbors and (optionally) the destination's long and short address. When the Graph Id value is less than 0x0100 it indicates a Superframe ID, and when equal to OxFFFF it indicates the Graph is Invalid. Subsection 9.2.5 It is important that the highest priority, oldest packet is the first forwarded. The age of the packet must be judged based on the ASN Snippet not when the device received the packet. Consequently, The discussion of the PacketTimeStamp must be deleted from the text and Table 9. Subsection 9.2.5 is modified to read as follows all devices must maintain a list of packet buffers These buffers are used to receive, process and transmit packets. The record associated with a packet is indicated in table 9. The Packet Id is used Page 3 of8 Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 to reference the packet and is created when the packet is added via the TRaNSMit request service primitive. I The ASN Snippet( see the Network Management Specification)is used to select the packet to transmit when either of two equal priority packets can be propagated in the same absolute slot. In this case the older packet is sent first. Also, in worst-case scenarios after a long time elapses, by comparing to MaxPacketAge, the asn Snippet is used to automatically flush a very old packet In addition, the record contains the packet's priority and the specification of the packet's destination Table 9. Packet record Content Description Packeted Unique Packet ID Payload The Data-Link Pay load (i.e. the NPDu) Priority Transmit priority of the packet Packet BirthASN Determines the age of the packet(based on the NPDU ASNSnippet) Destination Graph, source or proxy routing information or broadcast destination Subsection 9.2.5/Table 10 It is important that the highest priority, oldest packet is the first forwarded. The age of the packet must be judged based on the ASN Snippet. Consequently Table 10 is modified to read as follows Table 10. packet precedence order Tie-Breaker Rule Number (Apply Top-to Bottom until a single packet is identified) 0 Choose the packet(s)with the highest priority Choose the oldest packet based on the asn Snippet(see the Network management Specification) Choose the packet destined to the neighbor communicated with longest ago If keep alive time has expired with a neighbor, generate a keep alive packet to the neighbor with communicated with longest ago 4 If an advertise time has lapsed(see Subsection 9.3.4) then generate an Advertise packet. Subsection 9.3.2 Unless there is a transmit link to be serviced in the same slot all receive links must be serviced This must be clarified in the Subsection 9.3.2. Consequently, Subsection 9.3. 2 must be changed as follows For each active superframe, all receive links will be scheduled. The set of upcoming receive lir can be calculated in the same fashion as with transmit links(see Subsection 9.3.1). The main S difference is that, baring the need to propagate a packet, all receive links must be serviced. Once the ordered list of links is Page 4 of 8 Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 Subsection 9.3.3/Tablel1 For clarity, Sets of BoCntr values for BOExp =5, 6, 7 must be included in Table 11. Consequently Table 1 l is enhanced as follows BOExp Set of Possible Values for BOCntr 123 0,1} 0,1,2,3} {0,1,2,3,4,5,6,7} {0,1,2,3,4,5 12,13,14,15 567 0,1、2,3,4,5,,,28,29,30.31 {0,1,2,3,4,5,,,,60,61,62.63 f0,1,2,3,4,5,,124,125、126,1271 Subsection 9.3.4 Transmitting a Keep-Alive is more important than advertising. The requirement to use an Advertisement dlPdU in place ofa Keep-Alive is too complicated and must be stricken Consequently, Subsection 9. 3. 4 is modified to read as follows Nodes that are already part of the network may be configured by the Network manager to advertise the network and facilitate joining of new devices. The advertiseInterval attribute sets the interval at which Advertise packets(see Subsection 8. 2. 4)are generated. Whenever the Advertiselnterval lapses an Advertise packet shall be transmitted on the first available non-shared transmit link.When AdvertiseInterval is set to zero then an advertise packet shall be generated whenever a non-shared transmit link is available An advertise packet may be sent on any non-shared transmit link that is not in use. All other traffic has higher priority than advertising Page 5 of8 Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 Subsection 9.4.1/Figure 15 The state transition from listen to Iale with the event: Message Discarded & ( Destination = Broadcast) must be corrected. The correct event is simply Message Discarded. In addition another state transition must be added from from Listen to Idle with the event: Message Not Accepted & (Destination --Broadcast)(e.g, due to flow control in buffers Join SetTimeout && XMIT Successful &8 Link ==RX)&&(Link!F T> Desirialori = Broducdsl set rxDelEyB ISRXUiSET TRANSMIT Confirm(Success) et RxWait TsTxWait Talk NoRI XMIT Schedule Link Schedu Message Accepted & Desination== Broad. ast LIsten TRANSMIT, indic ate Destination I= Broadcast Set RxWait= TsAckWait ssage NOT Ar: [Alert民 IDLE Return packet to tx Queue (Destination = Broadcast Schedule link Schedule Lin k Wait for ack Me ssage Discarded TRANSMIT confirm(Success) Schedule link Nes sage Acepted & Message NOT Accepted & (Destination I= Br TRANSMIT indicate Set AcK Rc error Set ACK RC=Success Schedu le link Modification of Link or Superframe Answer FLUSH request TRANSMIT request Add Packet to Tx Queue Schedule link Schedule link FLUsH confIrm Figure 15. TDMA State Machine Page 6 of8 Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 Subsection 9. 4.3/Figure 18 The receive State Machine in figure 18 must be corrected to indicate all valid receive packets(even if they are not addressed to the device) must update the neighbor table. Currently, the state machine (incorrectly) indicates a packet not addressed to the device is immediately discarded. In reality that packet must still be validated and the neighbor table updated accordingly ENABLE request(Rx, Ch) Wait~ForRxStart Start rxN ait Til Listen for Packet ENABLE indicate Record Messge Start Time Receive Packet Validate par crement Bad Packet Counter Indicate Nc Response &3 Good MIC ncrement Rad MIC Counter Calculate Timing Error value Indicate No Response dicate Packet Type Update Neighbor labe Figure 18. Receive State machine Subsection io./table 12 In Table 12 In table 1 modify the tsrxackDelay entry as follows TSRXAck Delay End of message to when transceiver must be listening for ACK 800us±100us ge 7 of 8 Addendum To TDMA Data-Link Layer Specification(HCF SPEC-075) May17,2008 This page intentionally left blank Page 8 of8

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