Slave node for CAN bus network
First Claim
Patent Images
1. A Controller Area Network (CAN) bus system, comprising:
- a master node comprising a master controller unit and an external crystal oscillator, wherein the external crystal oscillator generates a clock signal used by the master controller unit to generate an internal, master node CAN clock signal;
at least one slave node comprising a slave controller unit, wherein the slave node does not include and is not coupled to an external crystal oscillator, and wherein the slave controller unit generates, internally, a slave node CAN clock signal; and
a CAN bus coupling the master node and the at least one slave node and enabling communications therebetween,wherein the at least one slave node monitors the CAN bus, analyzes frames transmitted over the CAN bus for a predetermined fixed pattern, and uses the predetermined fix pattern to generate the slave node CAN clock signal.
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Abstract
A CAN bus system that permits a slave node to be connected to the CAN bus. The slave node uses a preamble of a data frame transmitted by the master node on the bus to generate an internal CAN sampling clock. The slave node over-samples frames transmitted over the bus, and monitors the sampled data for a predetermined pattern, which is used to generate the slave node CAN sampling clock. Thus, the slave node does not require or include an external crystal for generating its CAN sampling clock.
18 Citations
19 Claims
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1. A Controller Area Network (CAN) bus system, comprising:
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a master node comprising a master controller unit and an external crystal oscillator, wherein the external crystal oscillator generates a clock signal used by the master controller unit to generate an internal, master node CAN clock signal; at least one slave node comprising a slave controller unit, wherein the slave node does not include and is not coupled to an external crystal oscillator, and wherein the slave controller unit generates, internally, a slave node CAN clock signal; and a CAN bus coupling the master node and the at least one slave node and enabling communications therebetween, wherein the at least one slave node monitors the CAN bus, analyzes frames transmitted over the CAN bus for a predetermined fixed pattern, and uses the predetermined fix pattern to generate the slave node CAN clock signal. - View Dependent Claims (2, 3, 4)
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5. A slave node for a Controller Area Network (CAN) bus system, the slave node comprising:
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a slave controller unit that processes data frames generated by a master node connected to a CAN bus, and generates its own data frames for transmission over the CAN bus, wherein the slave controller unit generates, internally, a CAN clock signal and operates in accordance with the CAN clock signal; and a CAN transceiver for connection to the CAN bus, and connected to the slave controller unit, wherein the CAN transceiver (i) receives the data frames transmitted over the CAN bus by the master node and provides said data frames to the slave controller unit, and (ii) provides the data frames generated by the slave controller unit to the CAN bus for transmission there-across, wherein the generated CAN clock signal permits the slave node to operate at a same effective baud rate as the master node, and wherein the slave node is not connected to an external crystal oscillator for generation of the CAN clock signal. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of operating a slave node connected to a Controller Area Network (CAN) bus, wherein one or more master nodes and one or more slave nodes are connected to the CAN bus, each master node has an external crystal oscillator for generating its CAN clock signal, and none of the slave nodes includes an external oscillator for generating their respective CAN clock signals, the method comprising:
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receiving CAN data transmitted over the CAN bus; sampling the received data, using an oscillator clock signal generated with an internal oscillator, for a predetermined fixed pattern; upon detection of the predetermined fixed pattern, counting edges of the bits of the data defining the predetermined fixed pattern using the oscillator clock signal to determine a divisor D; generating a local CAN clock signal using the divisor D, the oscillator clock signal, and a constant L, wherein D and L are greater than 1; and using the local CAN clock signal to process data frames, wherein the local CAN clock signal permits the slave node to operate at a same effective baud rate as the one or more master nodes. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification