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Questions and Answers
What is the maximum size of useful data that can be transmitted in a single frame?
What is the maximum size of useful data that can be transmitted in a single frame?
How is the priority of a message determined in the DeviceNet protocol?
How is the priority of a message determined in the DeviceNet protocol?
What is the primary purpose of the identifier coded on 11 bits at the start of the message?
What is the primary purpose of the identifier coded on 11 bits at the start of the message?
Which of the following is NOT a standard service provided by the DeviceNet Application layer?
Which of the following is NOT a standard service provided by the DeviceNet Application layer?
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What is the primary purpose of network administration in the DeviceNet protocol?
What is the primary purpose of network administration in the DeviceNet protocol?
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What is the mechanism used to transmit high-volume parameter data in the DeviceNet protocol?
What is the mechanism used to transmit high-volume parameter data in the DeviceNet protocol?
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What is the primary function of the Source MAC ID in DeviceNet?
What is the primary function of the Source MAC ID in DeviceNet?
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Which type of message is represented by the Message ID 1 1 0 1 0 1 1 1 0?
Which type of message is represented by the Message ID 1 1 0 1 0 1 1 1 0?
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What is the purpose of DeviceNet profiles?
What is the purpose of DeviceNet profiles?
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What is the role of the Group 1 Message ID in DeviceNet?
What is the role of the Group 1 Message ID in DeviceNet?
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Which message is used to acknowledge a change of state or cyclic message?
Which message is used to acknowledge a change of state or cyclic message?
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What is the significance of the DeviceNet node being modelled as a collection of objects?
What is the significance of the DeviceNet node being modelled as a collection of objects?
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What was the primary reason for the decline in prices of drivers and micro-controllers featuring CAN in the 1983-1987 period?
What was the primary reason for the decline in prices of drivers and micro-controllers featuring CAN in the 1983-1987 period?
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What was the main purpose of creating the ODVA in 1995?
What was the main purpose of creating the ODVA in 1995?
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What is the primary function of the DeviceNet protocol in industrial automation?
What is the primary function of the DeviceNet protocol in industrial automation?
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Which organization developed and launched DeviceNet products in 1993-1994?
Which organization developed and launched DeviceNet products in 1993-1994?
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What is the relationship between CAN 2.0 A and B, and ISO 11898?
What is the relationship between CAN 2.0 A and B, and ISO 11898?
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What is the name of the specifications document that defines the communication profile for DeviceNet?
What is the name of the specifications document that defines the communication profile for DeviceNet?
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Study Notes
DeviceNet History
- 1983-1987: Prices of CAN-based drivers and micro-controllers decreased due to high volume use in the automotive industry.
- 1993-1994: Allen Bradley (Rockwell Automation Group) developed and launched DeviceNet products.
- 1995: Open DeviceNet Vendor Association (ODVA) was created to promote and provide technical support for the DeviceNet specification.
- 1997: ODVA had approximately 200 member companies and offered over 100 different products.
- 2002: ODVA started developing specifications for integrating safety components.
DeviceNet Communication Model
- The principle of dominant and recessive bits enables non-destructive bit-by-bit arbitration in case of a collision.
- Message priority is indicated by the value of the identifier, with the lowest value having priority.
- Communication model is based on Producer/Consumer, where an 11-bit identifier informs receivers about the type of data in each message.
- Each receiver decides whether to accept the data, allowing multiple communication models.
DeviceNet Link Layer
- Maximum useful data size per frame is 8 bytes.
- Fragmentation is possible if more than 8 bytes are required.
- Transmission security is high due to numerous signalling and error detection devices.
DeviceNet Application Layer
- Three types of standard services are provided:
- Network administration: parameter settings, start-up, monitoring (master-slaves).
- Transmission of low-volume process data in real-time: I/O messages.
- Transmission of high-volume parameter data (> 8 bytes) by segmentation without time restrictions: explicit messages in client/server mode.
DeviceNet Identifier Allocation
- Identifiers are allocated using a specific bit structure, with different bits indicating different types of messages, such as:
- Message ID
- Source MAC ID
- Slave's I/O Bit-Strobe Response Message
- Destination MAC ID
DeviceNet Profiles
- DeviceNet uses object type modelling for:
- The list of available communication services.
- Device characteristics.
- A standard means of describing how to access internal variables of a product.
- A DeviceNet node is modelled as a collection of objects.
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Description
Learn about the basics of the CAN bus protocol, including message priority, identifier structure, and communication models. Understand how devices on the bus negotiate access and ensure data integrity.
