Protocols - Part B

Flashcards covering key concepts from the Protocols - Part B module, including HART, Foundation Fieldbus, and DeviceNet protocols.

What are the three fieldbus communication standards common in industrial settings?

Highway Addressable Remote Transducer (HART), Foundation Fieldbus, and DeviceNet.

What is the Highway Addressable Remote Transducer (HART) protocol?

An open fieldbus protocol released in 1989 that enables duplex digital communication and is compatible with 4 mA to 20 mA analog signaling.

Which layers of the OSI model does the HART Communications Foundation specify compliance with?

Physical layer, data link layer, and application layer.

What are the specifications defined by the HART physical layer of the OSI model?

Electrical signalling method, network topology, and cabling.

What standard does HART protocol use for digital communication, and what are its specifications?

Bell 202 FSK modem standard, with 1200 baud, eight data bits, odd parity, and one stop bit.

What is the address requirement for field devices using simultaneous analog/digital signalling in HART?

The address of the field device must be set to zero.

What is the address range for HART field devices configured for digital-only signalling?

An address between 1 and 15.

What are the two physical connection topologies supported by the HART network?

Point-to-point and multidrop bus.

What is the loop resistance requirement for HART connections?

A minimum loop resistance of 230 Ohms and a maximum of 1100 Ohms.

What is a key requirement for devices in a HART multidrop bus configuration?

All field devices must be configured for digital-only signaling with a unique, non-zero address from 1 to 15.

What is the maximum recommended number of devices practically connected to a HART single bus segment in multidrop configuration, and why?

No more than three or four devices, due to current limitations and diminishing scan rates.

What cabling is generally recommended for HART field segments?

Shielded twisted pair (STP) cabling, although unshielded twisted pair (UTP) can be used for short segments in low noise environments.

What specifications are defined by the HART data link layer of the OSI model?

Network access method, message frame structure, error detection, and device addressing.

What are the two network access methods used by the HART protocol?

Master/slave access method (poll/response) and burst mode access method (unsolicited messaging).

What is a key characteristic of HART field devices regarding communication initiation?

HART field devices are always slaves and do not communicate with the master unless commanded to do so.

What is the main advantage and limitation of the burst mode access method in HART?

Advantage: Significantly faster scan rates. Limitation: can only be used with point-to-point topology.

Name three categories of useable commands defined by the HART application layer specification.

Universal commands, common practice commands, and device-specific commands.

What is the purpose of universal commands in HART protocol?

To ensure a basic level of compatibility with other HART devices. These are standard command codes that must be included in every HART compliant device.

What is the initial purpose of FOUNDATION Fieldbus unlike other fieldbus protocols?

It was intended as an open standard from its inception.

What are the two different types of networks used by the FOUNDATION Fieldbus standard.

FOUNDATION Fieldbus high speed Ethernet (HSE) for controller-level communication, and FOUNDATION Fieldbus H1 for field-level communication.

What standard does FOUNDATION Fieldbus H1 use to define its physical layer characteristics?

IEC-61158-2 standard.

What electrical signalling method is used by FOUNDATION Fieldbus H1 segments?

Manchester Biphase-L.

What is the data rate used by FOUNDATION Fieldbus H1?

31.25 kbps.

What is the operational voltage range for power transmitted to field devices in Foundation Fieldbus H1?

Between 9V and 32V dc.

What is the maximum number of devices can connect to each segment in FOUNDATION Fieldbus H1?

A maximum of 32 devices can connect to each segment.

What is the function of a FOUNDATION Fieldbus linking device (FFLD)?

A network gateway that allows one or more H1 segments to connect to a high speed Ethernet (HSE) network or a proprietary controller backplane.

What device types are defined by the FOUNDATION Fieldbus H1 data link layer?

Link masters and basic devices.

What address range is typically assigned to commissioned field devices in FOUNDATION Fieldbus H1?

17 to 247 (11h to F7h).

What two basic network access methods are combined in FOUNDATION Fieldbus H1 segments?

Master/slave (command/response) messaging and token passing messaging.

What is the purpose and function of Resource Blocks (RB) in Foundation Fieldbus H1 field devices?

Stores and communicates hardware specific information about the field device.

What is DeviceNet protocol based upon for its physical layer?

ISO 11898-2 standard.

What organization manages DeviceNet and other CIP-based protocol specifications?

Open DeviceNet Vendors Association (ODVA).

What baseband electrical signalling is used to designed the DeviceNet physical layer?

Controller Area Network (CAN) network specification.

What data rates can be used on a DeviceNet segment?

125 kbps, 250 kbps, and 500 kbps.

What is meant when describing DeviceNet cabling using a two-pair wiring system (conductors)?

One pair is for data transmission and the other pair supplies power to field devices.

What are the most common cable types used for DeviceNet segments?

Thick round cables, thin round cables, and flat cables.

What are typical parameters in consideration for the overall DeviceNet specifications?

Maximum trunk line length and maximum cumulative drop line length.

What is the nominal impedance for the data pair in any DeviceNet cabling segment?

120 Ohms.

What voltage rating must power supplies used for DeviceNet segments have?

24 V.

What type of network gateway is responsible for controlling all communication with connected field devices in a DeviceNet segment?

DeviceNet scanner.

What is the maximum number of field devices that can connect to a DeviceNet segment (not including the scanner)?

63

Name two types communications managed by the scanner module during the scanner controlled messaging period.

Polled Messaging and Strobed Messaging.

Name the two of the methods that can be used by field devices during the inter-scan delay (ISD) period.

Change of state (COS) messaging and cyclic messaging.