Selective bit error detection at a bus device
View Patent ↗In one aspect, a data transmission rate of a message signal representing a bus message at a bus and a propagation delay between an occurrence of the message signal at a transmission output to the bus and an occurrence of the message signal at a receive input from the bus are determined. Bit error detection is selectively disabled responsive to a compatibility between the data transmission rate and the propagation delay. In another aspect, a bus line interface includes a transmit output and a receive input coupled to a bus line, a bit error detection module and a data rate module. The bus line interface also includes a bit error control module to selectively disable the bit error detection module based on a propagation delay between a signal and a reflected signal and based on a data transmission rate of the signal.
1. A method comprising:
determining, at a bit error module of a device coupled to a bus, a data transmission rate of a message signal representing a bus message;
determining, at the bit error module, a propagation delay between an occurrence of the message signal at a transmission output to the bus and an occurrence of the message signal at a receive input from the bus; and
selectively disabling bit error detection at the device responsive to a comparison of the data transmission rate to the propagation delay.
2. The method of claim 1 , wherein determining the data transmission rate of the message signal comprises determining a number of cycles of a clock signal between a first edge event and a second edge event of a synchronization field of the bus message, wherein the number of cycles is representative of the data transmission rate.
3. The method of claim 1 , wherein determining the propagation delay comprises determining a number of cycles of a clock signal between an occurrence of an edge event of the message signal at the transmission output and an occurrence of the edge event of the message signal at the receive input.
4. The method of claim 1 , wherein bit error detection comprises:
concurrently sampling, based on a sampling clock signal, the message signal at the transmission output to provide a first sample value and the message signal at the receive input to provide a second sample value, wherein a period of the sampling clock signal is based on the data transmission rate; and
determining a bit error based on a comparison of the first value to the second value, wherein a mismatch between the first value and the second value indicates a bit error.
5. The method of claim 4 , wherein selectively disabling bit error detection comprises:
enabling bit error detection when the propagation delay is less than a portion of the period of the sampling clock signal; and
disabling bit error detection when the propagation delay is greater than the portion of the period of the sampling clock signal.
6. A method comprising:
receiving, at a bus line interface of a device, a message signal representing a message header having a synchronization field, wherein the synchronization field is representative of a data transmission rate of the message signal;
determining a first value based on the synchronization field, wherein the first value is representative of the data transmission rate of the message signal;
determining a second value based on a number of clock cycles between an occurrence of an edge event in a first representation of the message signal present at a transmit output of the bus line interface and the occurrence of the edge event in a second representation of the message signal present at a receive input of the bus line interface, wherein the second value is representative of a propagation delay between the transmit output and the receive input; and
selectively disabling bit error detection at the device based on a comparison of the first value to the second value.
7. The method of claim 6 , wherein selectively disabling bit error detection comprises:
enabling bit error detection at the device responsive to the comparison of the first value to the second value indicating that the propagation delay is compatible with the data transmission rate; and
disabling bit error detection at the device responsive to the comparison of the first value to the second value indicating that the propagation delay is incompatible with the data transmission rate.
8. The method of claim 6 , further comprising:
comparing each value of a first sequence of values sampled at the transmit output with the corresponding value of a second sequence of values sampled at the receive input, wherein a sampling frequency of the transmit output and the receive input is based on the data transmission rate; and
providing an asserted bit error signal responsive to a substantial mismatch between a value of the first sequence of value and the corresponding value of the second sequence and responsive to bit error detection being enabled.
9. The method of claim 8 , further comprising:
providing an unasserted bit error signal responsive to bit error detection being disabled.
10. The method of claim 6 , wherein:
determining the first value comprises determining a first number of cycles of a clock between edge events of the synchronization field, wherein the first value is based on the first number of cycles; and
determining the second value comprises determining a second number of cycles of the clock between the occurrence of the edge event in the first representation of the message signal and the occurrence of the edge event in the second representation of the message signal, wherein the second value is based on the second number of cycles.
11. The method of claim 6 , wherein the bus is compliant with a Local Interconnect Network (LIN) standard.
12. A device comprising:
a bus line interface having a transmit output coupled to a bus line and a receive input coupled to the bus line, wherein a signal at the transmit output occurs at the receive input as a reflected signal;
a bit error detection module coupled to the bus line interface;
a data rate module coupled to the bus line interface, the data rate module to determine a data transmission rate of the signal based on a synchronization field of the signal; and
a bit error control module coupled to the bus line interface, the bit error detection module, and the data rate module, the bit error control module to selectively disable the bit error detection module based on a propagation delay between the signal and the reflected signal and based on the data transmission rate.
13. The device of claim 12 , wherein the bus line comprises a single bus line.
14. The device of claim 13 , wherein the bus line is compliant with a Local Interconnect Network (LIN) standard.
15. The device of claim 12 , wherein the bit error control module is configured to:
enable the bit error detection module responsive to the propagation delay being compatible with the data transmission rate; and
disable the bit error detection module responsive to the propagation delay being incompatible with the data transmission rate.
16. The device of claim 12 , wherein the bit error detection module is configured to:
compare each value of a first sequence of values sampled at the transmit output with the corresponding value of a second sequence of values sampled at the receive input, wherein a sampling frequency of the transmit output and the receive input is based on the data transmission rate; and
provide an asserted bit error signal responsive to a substantial mismatch between a value of the first sequence of value and the corresponding value of the second sequence and responsive to the bit error detection module being enabled.
17. The device of claim 12 , wherein the bit error detection module is configured to:
provide an unasserted bit error signal responsive to the bit error detection module being disabled.
18. The device of claim 12 , wherein the bit error control module is configured to:
determine a first number of cycles of a clock between edge events of the synchronization field, wherein the data transmission rate is determined based on the first number of cycles.
19. The device of claim 18 , wherein the bit error control module is configured to:
determine a second number of cycles of the clock between the occurrence of an edge event in the signal and the occurrence of the edge event in the reflected signal, wherein the propagation delay is determined based on the second number of cycles.