Method and device to wake-up nodes in a serial data bus
View Patent ↗A method of communication comprising sending communication signals switched between dominant and recessive values at clock intervals in frames over a serial data bus from at least one of a plurality of sending nodes to a plurality of receiving nodes. The receiving nodes have an operational state and a standby state in which the current consumption of the node is reduced compared to the operational state. The receiving nodes include wake-up trigger means for triggering transition from the standby state to the operational state in response to the communication signals. The frames of the transmitted signals include an identifier field during which the communication signal alternates between the dominant and recessive values in successive clock intervals with at least one significant occurrence during which the communication signal remains at one of the dominant and recessive values during at least two successive clock intervals, and the trigger means is selectively responsive to the position of the occurrence within the identifier field for triggering the transition from the standby state to the operational state.
1. A method of communication in a multi-master system comprising:
sending communication signals switched between dominant and recessive values at clock intervals in frames over a serial data bus from at least one of a plurality of sending nodes to a plurality of receiving nodes said frames including an identifier field, and said receiving nodes having an operational state and a standby state in which the current consumption of the node is reduced compared to said operational state, said receiving nodes including wake-up trigger circuitry for triggering transition from said standby state to said operational state in response to said communication signals;
wherein said identifier field includes at least one position at which said communication signal remains at said recessive value during at least two successive clock intervals so as to define an identifier code, and said trigger circuitry is selectively responsive to said position for triggering said transition from said standby state to said operational state, the trigger circuitry of at least one of said receiving nodes being responsive to more than one different identifier code so as to be capable of being triggered by any one of a plurality of sending nodes.
2. A method of communication as claimed in claim 1 , wherein said receiving nodes include clock circuitry for generating an internal clock signal and said trigger circuitry responds selectively to communication signals in which said position corresponds to a number of intervals defined by said internal clock signal and corresponding to an identifier value stored in said trigger circuitry.
3. A method of communication as claimed in claim 2 , wherein said frames include, before said identifier field, a synchronisation field in which said communication signal alternates between said dominant and recessive values, and said trigger circuitry is responsive to said synchronisation field for controlling a phase of said clock signal.
4. A method of communication as claimed in claim 1 , wherein said trigger circuitry is selectively responsive to said position if said communication signal remains at said recessive value during at least two successive clock intervals and changes to the dominant value in the following clock interval.
5. A method of communication as claimed in claim 1 , wherein said trigger circuitry is selectively responsive to said position if said communication signal remains at said recessive value during at least two successive clock intervals having changed from the dominant value in the preceding clock interval.
6. A method of communication as claimed in claim 1 , wherein said frames of said communication signals comprise a data field, said identifier field preceding said data field.
7. A method of communication as claimed in claim 6 , wherein during said data field said communication signal alternates between said dominant and recessive values in successive clock intervals with at least one position at which said communication signal remains at one of said dominant and recessive values during at least two successive clock intervals.
8. A method of communication as claimed in claim 1 , which is in conformity with Controller Area Network (CAN) standard.
9. A method of communication as claimed in claim 1 , wherein said trigger circuitry is selectively responsive to said position if said communication signal remains at said recessive value during at least two successive clock intervals and changes to the dominant value in the following clock interval having changed from the dominant value in the preceding clock interval.
10. A method of communication comprising
sending communication signals switched between dominant and recessive values at clock intervals in frames over a serial data bus from at least one of a plurality of sending nodes to a plurality of receiving nodes, said frames including an identifier field, and said receiving nodes having an operational state and a standby state in which the current consumption of the node is reduced compared to said operational state, said receiving nodes including wake-up trigger circuitry for triggering transition from said standby state to said operational state in response to said communication signals;
wherein said identifier field includes at least one position at which said communication signal remains at one of said dominant and recessive values during at least two successive clock intervals so as to define an identifier code, and said trigger circuitry is selectively responsive to said position for triggering said transition from said standby state to said operational state;
wherein said frames of said communication signals comprise a data field, said identifier field preceding said data field, and
wherein during said data field said communication signal alternates between said dominant and recessive values in successive clock intervals with at least one position at which said communication signal remains at one of said dominant and recessive values during at least two successive clock intervals.
11. A method of communication as claimed in claim 10 , wherein said receiving nodes include clock circuitry for generating an internal clock signal and said trigger circuitry responds selectively to communication signals in which said position in said identifier field corresponds to a number of intervals defined by said internal clock signal and corresponding to an identifier value stored in said trigger circuitry.
12. A method of communication as claimed in claim 11 , wherein said frames include, before said identifier field, a synchronisation field in which said communication signal alternates between said dominant and recessive values, and said trigger circuitry is responsive to said synchronisation field for controlling a phase of said clock signal.
13. A method of communication as claimed in claim 10 , wherein said trigger circuitry is selectively responsive to said position in said identifier field if said communication signal remains at said one of said dominant and recessive values during at least two successive clock intervals and changes to the complementary value in the following clock interval.
14. A method of communication as claimed in claim 10 , wherein said trigger circuitry is selectively responsive to said position in said identifier field if said communication signal remains at said one of said dominant and recessive values during at least two successive clock intervals having changed from the complementary value in the preceding clock interval.
15. A method of communication as claimed in claim 10 , which is in conformity with Controller Area Network (CAN) standard.
16. A method of communication as claimed in claim 10 , wherein said trigger circuitry is selectively responsive to said position in said identifier field if said communication signal remains at said recessive value during at least two successive clock intervals and changes to the dominant value in the following clock interval having changed from the dominant value in the preceding clock interval.