LonWorks - SNVT count

SNVT Name: SNVT_count
SNVT Index: 8

• The number of Data Array elements required i.e the data length for SNVT_count when specifying a Data Array name under a Map Descriptor is1.
  
• The value range allowed for this SNVT type is 0 .. 65,535 and the values outside this range will not be processed in a read or write on SNVT_count's value data item.
  
• The suggested data array format for SNVT_count is Uint16 i.e. 16-bit Unsigned Integer, Float format.
  
• Invalid value will always be "Not applicable" (N/A).
  
• SNVT_count contains only one data item named Event Count measured in counts only.

SNVT Index: 95

M10K Format

Introduction

The Modulo-10000 (M10K) format breaks a 32-bit value into two 16-bit registers, according to the following relationship:
High-Order Register = value 10000
Low-Order Register = value modulus 10000
The 32-bit value can be retrieved by the following calculation:
value = registerhigh x 10000 + registerlow

Example

Value 12345678 is passed in unsigned 32-bit Modulus-10000 format.
Registerhigh: 1234 = 04D2 Hex
Registerlow: 5678 = 162E Hex
value = 1234 * 10000 + 5678 = 12345678

Another Example

Value -12345678 is passed in signed 32-bit Modulus-10000 format.
Registerhigh: -1234 = FB2E Hex
Registerlow: -5678 = E9D2 Hex
value = -1234 * 10000 + -5678 = -12345678

CIP Motion, Safety & Advantages

What is CIP

CIP Motion

It is an extension to EtherNet/IP which enables integration of field devices and motion drives on the same network and at the same time purges the requirement for a separate motion optimized network. This gives lower system cost, improved system performance, and greatly reduced system complexity.

CIP Safety

It provides the capability to have a blend of safety devices and standard devices on the same network or wire for seamless integration and improved flexibility. The safety protocol provides fail-safe communication between nodes such as safety I/O blocks, safety interlock switches, safety light curtains and safety PLCs in safety applications up to Safety Integrity Level (SIL) 3 according to IEC 61508 standards.

Advantages

1. Coherent integration of I/O control, device configuration and data collection.
2. Seamless flow of information across multiple networks.
3. Ability to implement multi-layer networks without the added cost and complexity of bridges and proxies.
4. Minimized investment in system engineering, installation and commissioning.
5. Freedom to choose best of breed products, with the assurance of competitive prices and low integration cost.

LonWorks Glossary

Neuron ID

It is a address that is hardware dependent and changes according to the hardware. The network management tool must have the Neuron ID for commissioning a device. The Neuron ID does not contain any information about the device address. A unique 48 bit Neuron ID associated with each LonWorks device results in approximately 300 trillion different combinations when it gets burnt into the Neuron chip during the manufacturing process. When a device is pinned, the Neuron ID is broadcasted through the network so that a logical address (Subnet/Node ID) can be assigned.

Subnet/Node ID

Subnet is a logical collection that consists of up to 127 devices within a domain and all devices in a subnet must be on the same segment. With one subnet, the LNS Network Interface is assigned a Subnet/Node ID of 1/127, whereas all other device’s Subnet/Node IDs begin with an address of 1/1 and increase sequentially to 1/2, 1/3, etc. These values are automatically assigned by the network management tool. Up to 255 subnets can be defined within a single domain. Subnets cannot cross non-permanent type routers. The address is hardware independent i.e. whenever a device gets replaced; the new device uses the same Subnet/Node ID in spite of new one. The node ID identifies a device on a subnet. It is actually a logical address assigned to a device after it has been commissioned. The subnet segment of the ID is employed to route packets. Packets will be available to other channels/subnets only according to the requirement. The other channels include: the source channel, the destination channel and all channels between the source and destination. A device’s Neuron ID and Subnet/Node ID both can be found in the Identifiers tab of the device’s properties.

LNS (LonWorks Network Services)

LNS which is basically a client-server operating system developed by Echelon Corporation provides directory, installation, management, monitoring, and control services required for open LonWorks networks. It is a platform that permits multiple LNS applications to interoperate on the same personal computer (PC) or on multiple PCs on the same network. A single LNS Server can support many interoperating client applications. The LNS Server has the capability to work as a standalone application on a PC attached to the network, or on the same PC as the Network Management tool. Besides remote clients i.e. Clients on other PCs can log into the LNS Server to access the shared LNS database. API products cannot be commissioned using LNS tool and vice versa because API networks function as a peer-to-peer network and employ a different database structure than client-server model. Network Management tools using the client-server capabilities of LNS allow multiple Network Management tools running on different PCs to simultaneously access the same LNS Server. This capability allows several users to work at the same time on a single network. An application that uses the services of the LNS Server is called LNS client and the host application that uses an NSI as its network interface is called an LNS host application. This host application utilizes the services, events, and properties provided by an NSS to perform network installation, configuration, maintenance, repair, monitoring, and control. It can also implement its own application-specific services, events, and properties and, through the LNS architecture, make these available to other LNS host applications.

Lonworks Glossary II
Lonworks Glossary III

ControlNet - Data transfers

ControlNet supports both scheduled and unscheduled transfers.

Scheduled Transfer

Time critical data is scheduled data and deterministic and repeatable transfers that are continuous and asynchronous to the ladder logic program scan are called Scheduled data transfers. It occurs at a consistent rate that is either at the same or faster than the rate specified in an I/O map-table entry.

Unscheduled Transfer

Non-time critical data is unscheduled data and non-deterministic data transfers through ladder-initiated communication or programming devices are known as unscheduled transfers.A ControlNet network allows unscheduled messaging when deterministic delivery is not required. Unscheduled operations include unscheduled non-discrete I/O data transfers through ControlNet I/O Transfer instructions (CIOs)in the PLC ladder program and peer-to-peer messaging through Message instructions (MSGs) in the PLC ladder program. Unscheduled transfers are performed during the unscheduled time in the network update interval.  Number of nodes,application program, Network Update Time(NUT), etc. help determine how much time there is for unscheduled messaging.

Network Update Time (NUT)

It is the repetitive time interval in which data can be transmitted over the ControlNet network. Data cannot transfer faster than NUT.

Relay

A Relay is an electrically operated switch designed by Joseph Henry in 1835 with the capability of controlling an output circuit of higher power than the input circuit. An electromagnetic relay is simply an adaptation of an electromagnet. Current passing through the relay coil creates a magnetic field which attracts a lever and changes the switch contacts. A relay coil can be energized in following three ways:


1. Normally-open (NO) contacts 

They connect the circuit when the relay is activated and the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "make" contact.      












2.  Normally-closed (NC) contacts

They disconnect the circuit when the relay is activated and the circuit is connected when the relay is inactive. It is also called a Form B contact or "break" contact.














3. Change-over (CO), or double-throw (DT), contacts


 


They control two circuits i.e. one normally-open contact and one normally-closed contact with a common terminal. It is also called a Form C contact or "transfer" contact ("break before make"). Another type of contact that utilizes “make before break" functionality is called a Form D contact.


Application & Selection Criteria

LonWorks

LonWorks is not just a protocol or physical layer for communication but an exclusively designed networking technology platform to install, maintain, monitor and sense various automation and control applications. Essentially LonWorks was established for a range of automation functions within buildings such as lighting and HVAC. Invented by Echelon Corporation, the fundamental communications platform, twisted pair signaling technology, power line signaling technology, and IP tunneling method constitutes a global standard documented ISO/IEC 14908.                      
                     

LonWorks Protocol

A set of services is offered by the LonWorks Protocol that enables all devices in the network to transmit and receive messages to and from other devices via their application program— requiring no acquaintances with network topology or the other devices' names, addresses, or functions. Besides, LonWorks Protocol can be made to deliver authentic, high priority messages within delimited transaction times. Moreover Network management services allow remote network management tool’s interaction with devices over the network; making them capable to reconfigure network addresses and parameters, download application programs, report network problems and Start/stop/reset device application programs. Consequently it’s relatively easy to employ LonWorks network over any medium, including power line, twisted pair, radio frequency (RF), infrared (IR), coaxial cable, and fiber optics.  

BACnet School Part II

BACnet School Part I


DUPLICATE MAC ADDRESSES/DEVICE INSTANCE NUMBERS

What would happen if you had two BACnet MSTP devices with different MAC address but the same BACnet Device ID (Node ID) on the same network and you send a Broadcast Who-is message.
This would be an illegal configuration (no two devices shall have the same Device ID) but the rules for address binding say the last one wins. If new information arrives saying "I-AM Device 7? the old information is replaced.

To understand this answer you must know a thing or two about a token ring networks.

Basically a token ring networks works by passing a token around the network, whoever has the token may send message out, and when they are done with the token they pass it on to the next person in line.

For Example:

• Device A has the MAC address of 0x03
• Device B has the MAC address of 0x04
• Device C has the MAC address of 0x05
• Device A has the token
• Device A responses to any messages it got since the last time it got the token, then sends any custom messages it may have in queue
• Device A sends the token to device B
• Device B has the token
• Device B responses to any messages it got since the last time it got the token, then sends any custom messages it may have in queue
• Device B sends the token to device C
• Device C has the token
• Device C responses to any messages it got since the last time it got the token, then sends any custom messages it may have in queue
• Device C has the token but there is no one with a higher MAC address then Device C so Device C sends it's token to Device A
• Repeat

CAS BACnet Watchdog

"Who changed the set point? Why did that device stop?"

The BACnet protocol does not support authorization or authentication. Use our Watchdog tool to monitor where the commands that changed set points/device states came from. Our tool allows you to monitor some or all devices/objects/properties.

The CAS BACnet Watchdog records MAC addresses, IP address, messages and other information useful in tracking down unauthorized/unexpected commands. It's easy to install and easy to use.