08-03-2011, 02:11 PM
Presented by:
Ananya
Chetan Kumar
[attachment=9777]
CAN
Features:
• CAN is a serial bus system
• 2 or 4 CAN controllers and buses
• Data rates to 1 Mbits/second on each bus
• Compatible with CAN specification 2.0B, ISO 11898-1
• Multi-master architecture.
• Bus access priority determined by the message identifier(11- bit or 29-bit).
• Multicast and broadcast message facility.
• Data length from 0 up to 8 bytes.
• Powerful error handling capability.
Attributes of CAN
• Can is a serial bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously.
• In CAN network there is no addressing of stations, but instead prioritized messages are transmitted. A transmitter sends message to all CAN nodes (broadcast). Each node decides on the basis of the identifier received whether it should process the message or not. The identifiers also determines the priority that the message enjoys in competition for bus access.
• Each CAN message can transmit from 0-8 bytes of users information. Longer data information can be transmitted by using segmentation. Maximum transmission rate is specified as 1Mbits/s. This value applies to networks up to 40m. For distances up to 500m a speed of 125Kbits/s is possible, and for transmission up to 1Km a data rate of 50Kbits/s is permitted.
CAN Node Design:
• Each node consists of a microcontroller and a separate CAN
controller.
• CAN controller is interfaced to the twisted pair by a line driver and the twisted pair is terminated at either end by a 120ohm resistor.
• One important feature about the CAN node design is that the CAN controller has separate transmit and receive paths. So, as the node is writing on to the bus it is also listening back at the same time.
• In “CAN speak” a logic one is called a recessive bit and a logic zero is called a dominant bit. In all cases a dominant bit will overwrite a recessive bit. So, if ten nodes write recessive and one writes dominant, then each node will read back a dominant bit.
CAN Message Transmission:
• In the LPC2000, each CAN controller has a number of status and control registers plus three transmit buffers and a receive buffer. Once the CAN controller has been initialized, it is possible to transmit a message by writing to a transmit buffer. Each transmit buffer is made up of four words. Two words are used to hold the 8 bytes of data and one word holds the message identifier. The final register is the frame information register.
Bus Timing Register (CANBTR)
• • To configure CAN controller we must program the bit timing register. It is a protected register and may only be written to when the CAN controller is in reset. Bit zero of the mode register is used to place the CAN controller intoreset.
Ananya
Chetan Kumar
[attachment=9777]
CAN
Features:
• CAN is a serial bus system
• 2 or 4 CAN controllers and buses
• Data rates to 1 Mbits/second on each bus
• Compatible with CAN specification 2.0B, ISO 11898-1
• Multi-master architecture.
• Bus access priority determined by the message identifier(11- bit or 29-bit).
• Multicast and broadcast message facility.
• Data length from 0 up to 8 bytes.
• Powerful error handling capability.
Attributes of CAN
• Can is a serial bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously.
• In CAN network there is no addressing of stations, but instead prioritized messages are transmitted. A transmitter sends message to all CAN nodes (broadcast). Each node decides on the basis of the identifier received whether it should process the message or not. The identifiers also determines the priority that the message enjoys in competition for bus access.
• Each CAN message can transmit from 0-8 bytes of users information. Longer data information can be transmitted by using segmentation. Maximum transmission rate is specified as 1Mbits/s. This value applies to networks up to 40m. For distances up to 500m a speed of 125Kbits/s is possible, and for transmission up to 1Km a data rate of 50Kbits/s is permitted.
CAN Node Design:
• Each node consists of a microcontroller and a separate CAN
controller.
• CAN controller is interfaced to the twisted pair by a line driver and the twisted pair is terminated at either end by a 120ohm resistor.
• One important feature about the CAN node design is that the CAN controller has separate transmit and receive paths. So, as the node is writing on to the bus it is also listening back at the same time.
• In “CAN speak” a logic one is called a recessive bit and a logic zero is called a dominant bit. In all cases a dominant bit will overwrite a recessive bit. So, if ten nodes write recessive and one writes dominant, then each node will read back a dominant bit.
CAN Message Transmission:
• In the LPC2000, each CAN controller has a number of status and control registers plus three transmit buffers and a receive buffer. Once the CAN controller has been initialized, it is possible to transmit a message by writing to a transmit buffer. Each transmit buffer is made up of four words. Two words are used to hold the 8 bytes of data and one word holds the message identifier. The final register is the frame information register.
Bus Timing Register (CANBTR)
• • To configure CAN controller we must program the bit timing register. It is a protected register and may only be written to when the CAN controller is in reset. Bit zero of the mode register is used to place the CAN controller intoreset.
