Method for trimming an adjustable oscillator to match a CAN-bus and a CAN-bus communication controller

A method comprising:

• determining a measured number of cycles of an adjustable oscillator between a first signal and a second signal within a Controller Area Network (CAN) frame transmitted on a Controller Area Network-bus (CAN-bus);
• determining an information about a present cycle time of the adjustable oscillator using the measured number of cycles and a nominal number of cycles per bit time;
• and trimming a cycle time of an adjustable oscillator to match the CAN-bus operating with a predetermined bit time based on the determined information;
• adjusting the cycle time of the local oscillator when the measured number of cycles deviates from an integer multiple of the nominal number of cycles by more than a predetermined tolerance value,
• wherein the predetermined tolerance value is smaller than or equal to 0.4% of the nominal number of cycles.

A method for trimming a cycle time of an adjustable oscillator to match a Controller Area Network-bus (CAN-bus) operating with a predetermined bit time, comprising:

• detecting a first falling edge of a bit transmitted on the bus within a CAN-bus message;
• waiting for a predetermined number of cycles of the adjustable oscillator;
• detecting a second falling edge of a bit transmitted on the bus;
• and
• determining a measured number of cycles of the adjustable oscillator between the detection of the first falling edge and the second falling edge;
• determining a deviation between the measured number of cycles and an integer multiple of a nominal number of cycles per bit time;
• and
• adjusting the cycle time of the adjustable oscillator when the deviation is greater than a predetermined tolerance value, wherein adjusting the cycle time comprises increasing or decreasing the cycle time by a fixed value.

A method for trimming a cycle time of an adjustable oscillator to match a Controller Area Network-bus (CAN-bus) operating with a predetermined bit time, comprising:

• detecting a first falling edge of a bit transmitted on the bus within a CAN-bus message;
• waiting for a predetermined number of cycles of the adjustable oscillator;
• detecting a second falling edge of a bit transmitted on the bus;
• and
• determining a measured number of cycles of the adjustable oscillator between the detection of the first falling edge and the second falling edge;
• determining a deviation between the measured number of cycles and an integer multiple of a nominal number of cycles per bit time;
• and
• adjusting the cycle time of the adjustable oscillator when the deviation is greater than a predetermined tolerance value,
• wherein the predetermined tolerance value is smaller than or equal to 0.4% of the nominal number of cycles.

A method for accessing a Controller Area Network-bus (CAN-bus), comprising:

• repeating a method for trimming a cycle time of an adjustable oscillator until a deviation is determined to be smaller than or equal to the predetermined tolerance value, wherein the adjustable oscillator performs the method of:
• detecting a first falling edge of a bit transmitted on the bus within a CAN-bus message;
• waiting for a predetermined number of cycles of the adjustable oscillator;
• detecting a second falling edge of a bit transmitted on the bus;
• determining a measured number of cycles of the adjustable oscillator between the detection of the first falling edge and the second falling edge;
• determining the deviation between the measured number of cycles and an integer multiple of a nominal number of cycles per bit time;
• and
• adjusting the cycle time of the adjustable oscillator when the deviation is greater than a predetermined tolerance value;
• evaluating an error status of a message transmitted on the CAN-bus;
• transmitting messages to the CAN-bus only when the error status indicates no error, an acknowledgement error or an CRC error,
• while transmitting messages to the CAN-bus, determining the error status of a predetermined number of consecutive messages;
• and
• when the error status of all consecutive messages indicates an error:
• stop transmitting messages to the CAN-bus;
• and
• repeating the method for trimming a cycle time of an adjustable oscillator until the deviation is smaller than or equal to the predetermined tolerance value.

A Controller Area Network-bus (CAN-bus) communication controller for a CAN-bus operating with a predetermined bit time, comprising:

• an adjustable oscillator having an output coupled with an access unit to provide an operating clock signal for the access unit;
• an access unit comprising one or more terminals for signal lines of the CAN-bus, the access unit being adapted to detect a first signal and a second signal within a CAN-bus message transmitted on the CAN-bus, wherein the second signal is determined after waiting for a predetermined number of cycles of the adjustable oscillator after the detection of the first signal, wherein the predetermined number of cycles is a predefined integer multiple of a nominal number of cycles, the predefined integer multiple being equal to or smaller than a minimum number of bits of a message transmitted on the bus;
• and
• a controller module coupled to the adjustable oscillator and adapted to determine an information about a present cycle time of the local adjustable oscillator using a measured number of cycles of the adjustable oscillator between the first signal and the second signal and a nominal number of cycles per bit time, wherein the controller is further adapted to trim a cycle time of the adjustable oscillator to match the CAN-bus operating with a predetermined bit time based on the determined information about the present cycle time.