Subscriber station for a serial bus system, and method for communication on a serial bus system

1 . A subscriber station for a serial bus system, comprising:

a communication control device configured to control communication of the subscriber station with at least one other subscriber station of the bus system;

wherein:

a bit time in a first communication phase of the bus system can differ from a bit time in a second communication phase of the bus system;

the communication control device is configured to sample and evaluate, according to a predetermined frame format, a signal received from a bus of the bus system, the sampled signal being based on a transmit signal generated by another subscriber station;

the predetermined frame format includes a predetermined field that (a) indicates a transition from the second communication phase to the first communication phase and (b) includes two or three bits having a logical value of 1 between a beginning of the predetermined field and a following falling edge of the predetermined field;

during the evaluation, the communication control device is configured to determine that a sampled bit sequence of the sampled signal constitutes a valid instance of the predetermined frame format by recognizing the predetermined field as present and valid, independently of whether only one bit or two consecutive bits having the logical value 1 were sampled between the beginning of the predetermined field and the following falling edge of the predetermined field in the sampled signal; and

the communication control device is configured to perform synchronization at the falling edge of the predetermined field of the valid instance of the predetermined frame format in the sampled signal.

2 . The subscriber station as recited in claim 1 , wherein:

the predetermined field has four bits with the bit time of the first communication phase,

wherein the predetermined field has a bit sequence with a logical value 1101, and

wherein the communication control device is configured to, after sampling, in the sampled signal, a bit having the logical value 1 between the beginning of the predetermined field and the following falling edge of the predetermined field, evaluate a next bit which is sampled with a logical value 0 in the sampled signal and which is sampled at the latest for a third bit of an expected bit sequence 1101, as the third bit of the expected bit sequence 1101.

3 . The subscriber station as recited in claim 2 , wherein the communication control device is configured to evaluate a frame which the communication control device has sampled from the sampled signal as faulty when neither the first bit nor the second bit of the predetermined field was sampled as logic 1.

4 . The subscriber station as recited in claim 3 , wherein the communication control device is configured to evaluate a frame which the communication control device has sampled from the sampled signal as not faulty but valid with regard to the predetermined field:

i) when the first bit of the predetermined field was sampled as logic 0 and the second bit of the predetermined field was sampled as logic 1, or

ii) when the first bit of the predetermined field was sampled as logic 1 and the second bit of the predetermined field was sampled as logic 0.

5 . The subscriber station as recited in claim 3 , wherein the communication control device is configured to activate a hard synchronization or a synchronization when the first bit of the predetermined field is sampled as logic 1 or when the second bit of the predetermined field is sampled as logic 1.

6 . The subscriber station as recited in claim 1 , wherein the communication control device is configured to evaluate as faulty a frame which the communication control device has sampled from the sampled signal when the first bit of the predetermined field was not sampled as logic 1.

7 . The subscriber station as recited in claim 1 , wherein the communication control device is configured to activate a hard synchronization when the first bit of the predetermined field is sampled as logic 1.

8 . The subscriber station as recited in claim 1 , wherein:

the predetermined field has five bits with the bit time of the first communication phase,

the predetermined field has a bit sequence with a logical value 11101, and

the communication control device is configured to, after sampling a bit with the logical value 1 for a second bit of the bit sequence in the sampled signal, to evaluate a next bit that is sampled in the sampled signal with a logical value 0 and is sampled at the latest for a fourth bit of an expected bit sequence 11101, as the fourth bit of the expected bit sequence 11101.

9 . The subscriber station as recited in claim 8 , wherein:

in a frame which the communication control device has sampled from the sampled signal, the communication control device is configured to ignore a sampled value of the first bit of the predetermined field and to evaluate a random value for a third bit of the predetermined field as not faulty, and

the communication control device is configured to evaluate a frame which the communication control device has sampled from the sampled signal as faulty when the second bit of the predetermined field was sampled as logic 0.

10 . The subscriber station as recited in claim 8 , wherein the communication control device is configured to activate a hard synchronization when the second bit of the predetermined field is sampled as logic 1.

11 . The subscriber station as recited in claim 1 , further comprising:

a transceiver configured to transmit a transmit signal onto the bus of the bus system, and/or to receive the sampled signal from the bus of the bus system.

12 . The subscriber station as recited in claim 11 , wherein:

the communication control device is configured to generate the transmit signal, and

the communication control device is configured to signal to the transceiver using a pulse-width modulation in the transmit signal that the transceiver has to switch its operating mode to an operating mode for transmitting in the first communication phase or to an operating mode for transmitting in a second communication phase.

13 . The subscriber station as recited in claim 11 , further comprising:

a signal-improvement module configured to accelerate a transition on the bus in the first communication phase from a dominant bus level to a recessive bus level, which is able to be overwritten by the dominant bus level;

wherein the transceiver is configured to additionally activate the signal-improvement module for an acceleration of the transition from one of the bus levels of the second communication phase to the recessive level of the first communication phase when the subscriber station is a transmitter of the transmit signal onto the bus and the transceiver switches from an operating mode in which the communication control device transmits the transmit signal onto the bus of the bus system in the second communication phase, to an operating mode in which the communication control device transmits the transmit signal onto the bus of the bus system in the first communication phase.

14 . The subscriber station as recited in claim 1 , wherein:

the predetermined frame format is compatible with CAN FD, and

negotiations take place in the first communication phase as to which one of the subscriber stations of the bus system is given an at least intermittent exclusive, collision-free access to the bus in a following second communication phase.

15 . A bus system, comprising:

a bus; and

at least two subscriber stations which are connected to one another via the bus in such a way that they are capable of serially communicating with one another and of which at least one subscriber station includes a communication control device configured to control communication of the subscriber station with at least one other subscriber station of the bus system;

wherein:

a bit time in a first communication phase of the bus system can differ from a bit time in a second communication phase of the bus system;

the communication control device is configured to sample and evaluate, according to a predetermined frame format, a signal received from a bus of the bus system, the sampled signal being based on a transmit signal generated by another subscriber station;

the predetermined frame format includes a predetermined field that (a) indicates a transition from the second communication phase to the first communication phase and (b) includes two or three bits having a logical value of 1 between a beginning of the predetermined field and a following falling edge of the predetermined field;

during the evaluation, the communication control device is configured to determine that a sampled bit sequence of the sampled signal constitutes a valid instance of the predetermined frame format by recognizing the predetermined field as present and valid, independently of whether only one bit or two consecutive bits having the logical value 1 were sampled between the beginning of the predetermined field and the following falling edge of the predetermined field in the sampled signal; and

the communication control device is configured to perform synchronization at the falling edge of the predetermined field of the valid instance of the predetermined frame format in the sampled signal.

16 . A method for communication in a serial bus system, wherein a bit time in a first communication phase of the bus system can differ from a bit time in a second communication phase of the bus system, the method being executed using a subscriber station of the bus system which has a communication control device, the method comprising the following steps:

controlling, using the communication control device, a communication of the subscriber station with at least one other subscriber station of the bus system;

sampling, by the communication control device, a signal received from a bus of the bus system, the sampled signal being based on a transmit signal generated by another subscriber station;

evaluating, by the communication control device, the sampled signal according to a predetermined frame format, wherein the predetermined frame format includes a predetermined field that (a) indicates a transition from the second communication phase to the first communication phase and (b) includes two or three bits having a logical value of 1 between a beginning of the predetermined field and a following falling edge of the predetermined field, wherein, during the evaluation, the communication control device determines that a sampled bit sequence of the sampled signal constitutes a valid instance of the predetermined frame format by recognizing the predetermined field as present and valid, independently of whether only one bit or two consecutive bits having the logical value 1 were sampled between the beginning of the predetermined field and the following falling edge of the predetermined field in the sampled signal; and

performing, by the communication control device, synchronization at the falling edge of the predetermined field of the valid instance of the predetermined frame format in the sampled signal.