Network Variables for Model CM4 LONWORKS Protocol Version 1.2

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1 Zellweger Analytics, Inc. 405 Barclay Boulevard Lincolnshire, IL USA Tel: Fax: Toll-free: Technical Note Network Variables for Model CM4 LONWORKS Protocol Version Rev Introduction LONWORKS is a communications protocol developed by Echelon Corporation, which facilitates peer-to-peer communication in a control network. Each segment can contain up to 64 nodes and up to 2.7 Km of media. Routers permit expansion of the network to thousands of nodes. Models CM4 and CM4-P gas monitors are available with LONWORKS Interfaces. The CM4 LONWORKS interface device contains five LONMARK objects and 21 network variables. Object 0 is a node object while Objects 1-4 are open-loop sensors measuring gas concentration. Version 1.2 of this software includes a number of enhancements over V1.1, but retains significant compatibility. Improvements include: aggregate network variable output configurable send timers new network variable inputs to facilitate easier control of the instrument The new network variable and configuration inputs for V1.2 are shown in the LONMARK object diagram, Figure1. Other changes for V1.2 include the addition of an aliased address table. This permits a network variable output to be bound to multiple destinations without resorting to group addressing Page 1 of 8

2 CM4 LonMark Device Node Object nvirequest SNVT_obj_request nvireset (new) nvimonitor (new) ncimaxsendt (new) SNVT_elapsed_time nciminsendt (new) SNVT_elapsed_time nvo00status SNVT_obj_status nvo00faults SNVT_switch nvo00faultd nvo00alml nvoafstat (new) SNVT_state nvohrtbeat (new) SNVT_count OpenLoopSensor GasMonPt1 nvo01conc SNVT_ppm_f nvo01flow long nvo01alml OpenLoopSensor GasMonPt2 nvo02conc SNVT_ppm_f nvo02flow long nvo02alml OpenLoopSensor GasMonPt3 nvo03conc SNVT_ppm_f nvo03flow long nvo03alml OpenLoopSensor GasMonPt4 nvo04conc SNVT_ppm_f nvo04flow long nvo04alml Figure 1. LONMARK Object Diagram Page 2 of 8

3 Network Variable Details nvi00request accepts LONMARK commands to start or stop monitor and to reset faults. For more information on this network variable please see the LONMARK Application Layer Interoperability Guidelines and the SNVT Master List and Programmer s Guide. (For more information about LONWORKS, see or Refer to Table 1 for a list of implemented requests. Note that V1.2 software permits performing many of these operations with simpler variables nvimonitor and nvireset: Request Node 0 implementation Node 1-4 implementation 0 RQ_NORMAL start monitor start monitor 1 RQ_DISABLED exit monitor 2 RQ_UPDATE_STATUS retransmit status retransmit status 3 RQ_SELF_TEST 4 RQ_UPDATE_ALARM 5 RQ_REPORT_MASK notify of implementation notify of implementation 6 RQ_OVERRIDE 7 RQ_ENABLE start monitor 8 RQ_RMV_OVERRIDE 9 RQ_CLEAR_STATUS 10 RQ_CLEAR_ALARM clears all alarms, faults clears all alarms, faults Table 1. Implemented Requests nvo00status is the companion LONMARK NV for nvi00request. This conveys information about the CM4's monitoring status, the state of alarms and faults, and the point disable status. The object_id field will increment from 0-4 every 50 seconds as this NVO conveys information about all five objects inside the device. Note, in V1.2 software most of this information is available more conveniently in nvoafstat. See Table 2 for interpretation of nvo00status Page 3 of 8

4 LONMARK Field Name Node 0 interpretation Node 1-4 interpretation Bit position in LONMAKER Browser Hexadecimal representation of field in NVO object_id (16 bits) FFFF invalid_id object_id>4 object_id> invalid_request unimplemented unimplemented request made request made disabled out of monitor disabled by configuration or PntLockOn out_of_limits open_circuit out_of_service mechanical_fault instrument fault instrument fault feedback_failure over_range alarm 2 any pt alarm 2 this pt under_range electrical_fault maintenance maintenance (minor) fault (minor) fault unable_to_measure disabled by fault comm_failure fail_self_test host is dead host is dead self_test_in_progress locked_out manual_control in_alarm alarm 1 any pt alarm 1 this pt in_override report_mask mere capability report Table 2. Interpretation of nvo00status mere capability report nvo00faults of type SNVT_switch, reports the existence of any fault. The state byte of this two-byte structure will contain a FALSE (0x00) if no fault is active or a TRUE (0x01) if a maintenance or an instrument fault exists. The value byte will contain the fault number as defined in Appendix B of the CM4 Technical Handbook. Note, Echelon's tools often divide the value byte by two and present it as a float. For example if fault 39 ("loss of flow") is active then nvo00faults will have the value {0x27,0x01} but LONMAKER will display it as "19.5,1". This NVO indicates the precise cause of the fault to an HMI. For example, it would be possible to program an HMI to display "Transport Error" when nvofaults.value is 37. However, Zellweger Analytics may extend the fault list in future software revisions. nvo00faultd of type reports if a fault is active in a simpler format for use by control devices such as relay boxes. This has the value ST_OFF (0x00) normally, ST_LOW (0x01) if a maintenance fault exists or ST_MED (0x02) if an instrument fault exists Page 4 of 8

5 nvo0xalml (five variables) of type report the alarm state of the CM4. The four variables nvo01alml through nvo04alml convey the alarm level of the four points. The general alarm variable nvo00alml reports the highest alarm level on any point. ST_OFF (0x00) will be transmitted if no alarm exists. ST_LOW (0x01) means that a level 1 alarm exists, while ST_MED (0x02) corresponds to a level 2 alarm. nvo0xconc (four variables) report the concentration of the target gas on the four points. This is always in parts per million as a floating point number in accordance with LONMARK standards. nvo0xflow (four variables) reports the sample flow for each point. This is in cc/minute as a 16-bit integer and is updated every ncimaxsendt. Note that this number is rarely needed, as the CM4 checks for low flow internally. nvoafstat of type SNVT_state is new for V1.2 and reports alarm, fault and monitoring information in a highly condensed 16-bit format as follows: bit function F msb pt4 nc E D C B A lsb hb im FltStat Pt4Alm Pt3Alm Pt2Alm Pt1Alm pt3 nc pt2 nc pt1 nc The meaning of each of the two-bit point alarm and fault fields is as follows: Field Value (binary) PtxAlm meaning FltStat meaning 0,0 no alarm no fault 0,1 level 1 alarm maintenance fault 1,0 level 2 alarm instrument fault 1,1 not used not used Bit "im" (in monitor mode) is TRUE, if and only if the CM4 is in monitor mode. Bit "hb" (heartbeat) toggles every ncimaxsendt to indicate the CM4 is alive. Bits C - F "ptx nc" (no coverage) are TRUE, whenever the point is not capable of detecting gas because monitoring was stopped, the point was unconfigured or a fault occurred. These bits will go FALSE, if the point is monitoring normally. nvohrtbeat is a new variable of type SNVT_count for V1.2. This transmits every ncimaxsendt and increments approximately once per second if communication is working between the CM4 main microprocessor and the LONWORKS gateway. This facilitates verifying that the node is alive by external equipment such as a HMI. However, verification of node health may be available in the HMI low-level networking software, which may be preferable to this application-level verification Page 5 of 8

6 nvireset is a new variable of type for V1.2. This provides a more convenient mechanism for resetting the CM4 than nvirequest. Faults and alarms reset when this input makes a transition from ST_OFF (0x00) to a non-st_low, ST_MED, ST_HIGH, or ST_ON values. nvimonitor is another new variable of type for V1.2. This provides a more convenient mechanism for starting and stopping monitor than nvirequest. Monitoring will stop when this input is updated with ST_OFF. Monitoring will start when this input is updated with a non-st_off value. Other devices on the LONWORKS network must not update this NVI without cause, as this might overwrite commands given on the front panel or otherwise confuse the CM4. nciminsendt and ncimaxsendt are new network configuration inputs which permit adjusting the CM4's frequency of transmission. This facilitates achieving a balance between network loading and timely notification of events. The possible values of nciminsendt and ncimaxsendt are summarized in the following table: Parameter V1.1 V1.2 fixed value Minimum Default Maximum nciminsendt 1 sec 1 sec 2 sec 30 sec ncimaxsendt 50 sec 30 sec 60 sec 120 sec All NVOs are routinely sent every ncimaxsendt. Nvo0xFlow and nvohrtbeat are only propagated at this slow rate. Nvo00Status is sent with the fixed period of 10 seconds per report to cover the state of all five objects every 50 seconds. However, most NVOs are transmitted with the shorter nciminsendt period, if they are non-zero and one time after they become zero. This is intended to conserve network bandwidth under routine conditions while providing timely notification when a problem starts and stops. Additionally, it provides a highly redundant notification of a persistent problem. This scheme applies to nvofaults, nvofaultd, nvo0xalml, nvoafstat and nvo0xconc Page 6 of 8

7 Summary of the Upgrades from Version 1.1 to Version Four network variables have been added nvoafstat nvohrtbeat nvireset nvimonitor 2. Two network configuration inputs have been added ncimaxsendt nciminsendt 3. The alias address table size has been increased from 0 to 45 entries. This facilitates binding the network variable outputs of the CM4 to more than one destination without using group addressing. 4. The number of network output buffers has been increased from 4 to 14. This improves the multiprocessing of the neuron chip and reduces the probability of the neuron entering preemption mode. 5. A random boot-up delay of up to two seconds has been added. This staggers transmissions from otherwise identical CM4s to reduce collisions. 6. The LONMARK program ID has been incremented Page 7 of 8

8 LONWORKS and LONMARK are registered trademarks of Echelon Corp. Zellweger Analytics, Inc. 405 Barclay Boulevard Lincolnshire, IL For more information contact Zellweger Analytics Service Department during normal business hours at: or Hour Emergency Service Hotline: This publication is not intended to form the basis of a contract, and the company reserves the right to amend the design and specification without notice Page 8 of 8

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