Subscriber Station Frame Checksum Placement for Serial Bus Error Detection
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Solution Overview
Problem
Current serial bus systems, such as those using the CAN FD protocol, face issues with error detection due to variable frame lengths and the complexity introduced by 'stuff bit counters,' which reduce data transfer rates and increase error probabilities.
Innovation Solution
A subscriber station design that includes a communication control device generating frames with a fixed frame length field, eliminating the need for a 'stuff bit counter' and ensuring correct checksum placement, thereby enhancing error detection and increasing net data transfer rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If variable data field length is used in CAN FD to prevent bus blocking, then productivity is improved, but reliability deteriorates due to incorrect checksum placement when bit errors occur
Solution Approach 1:
The patent applies preliminary action by pre-defining a fixed maximum frame length in the frame structure. This allows the receiver to always know where the checksum is located (at the predetermined position), enabling reliable error detection even when the actual data field is shorter. The fixed frame structure is established in advance, preventing the reliability issue caused by variable lengths.
Solution Approach 2:
The patent changes the parameter of frame length from variable to fixed by introducing a maximum frame length that is predetermined. The data field can be shorter than this maximum, but the overall frame structure maintains a constant length, which stabilizes the checksum position and improves reliability while still allowing flexible data transmission.
2Adaptability or versatility
If stuff bit counter is implemented to handle dynamic bit stuffing, then adaptability is improved, but device complexity increases and net data rate decreases
Solution Approach 1:
The patent extracts and removes the stuff bit counter mechanism from the frame structure. By using a fixed maximum frame length, the system no longer needs to dynamically track and compensate for stuff bits, thereby reducing device complexity and eliminating the data overhead associated with the stuff bit counter while maintaining adaptability through the fixed frame approach.
3Adaptability or versatility
If stuff bit counter is used to record dynamically inserted stuff bits, then adaptability is improved, but productivity deteriorates due to data overhead reducing net data rate
Solution Approach 1:
The patent removes the stuff bit counter and its associated data overhead from the frame structure. By establishing a fixed maximum frame length, the system achieves adaptability for variable data lengths without needing to transmit additional information about stuff bits, thereby maintaining the net data rate and improving productivity.
4Reliability
If maximum frame length is predetermined to ensure correct checksum placement, then reliability is improved, but adaptability decreases due to potential bus blocking
Solution Approach 1:
The patent applies partial action by allowing the data field to be shorter than the maximum frame length when less data needs to be transmitted. The fixed maximum length provides the reliability needed for correct checksum placement, while the ability to use only the necessary portion maintains adaptability and prevents unnecessary bus blocking, achieving both goals simultaneously.
Data Source
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AI summary
The invention relates to a subscriber station (10; 30) for a serial bus system (1) and to a method for communication in a serial bus system (1). The subscriber station (10; 30) has a communication controller (11; 31) for controlling a communication of the subscriber station (10; 30) with at least one other subscriber station (10; 20; 30) of the bus system (1), and a transceiver (12; 32) for transmitting a transmission signal (TXD) generated by the communication controller (11; 31) to a bus (40) of the bus system (1), so that, for a message (45) which is exchanged between subscriber stations (10, 20, 30) of the bus system (1), the bit time (t_bt) of a signal transmitted to the bus (40) in the first communication phase (451) differs from a bit time (t_bt) of a signal transmitted in the second communication phase (452), the communication controller (11; 31) being configured to generate the transmission signal (TXD) according to a frame (450; 450_1; 4500), in which a field for a header checksum (H_CRC) and a field for a frame checksum (F_CRC) is provided, and the communication controller (11; 31) being configured to calculate the header checksum (H_CRC) from all bits in the header of a frame (450; 450_1; 4500) formed for the message (45), with the exception of fixed stuff bits which have been inserted into the header of the frame (450; 450_1; 4500) according to a fixed bit stuffing rule, according to which a fixed stuff bit is to be inserted after a fixed number of bits.