Circuitry for encoding a bus signal and associated methods

1. An apparatus comprising:

an input terminal for receiving an input signal indicative of signalling from a network, the input signal comprising at least a two level signal that comprises either a first voltage level or a second voltage level, an encoder configured to encode the input signal into an output signal and an output terminal for outputting the output signal, wherein the encoder is configured to:

detect a first edge in the input signal;

in response to the detection of the first edge provide a pulse generation sequence comprising the encoder being configured to:

generate, in the output signal, a first pulse, the first pulse comprising a first ramp portion in which the voltage level is changed from a first-pulse level to a second-pulse level, a first hold portion in which the second-pulse level is maintained, a second ramp portion in which the voltage level is changed from the second-pulse level to the first-pulse level and a second hold portion in which the first-pulse level is maintained, and wherein the first ramp portion and the first hold portion are provided at least over a first predetermined minimum time period and wherein the second ramp portion and the second hold portion are provided at least over a second predetermined minimum time period, and wherein the first pulse is provided over the first and second minimum time periods irrespective of an edge subsequent the first edge being present in the input signal; and

sample the input signal to obtain a first sample indicative of a voltage level of the input signal to which the input signal transitions following said detection of the first edge and store said first sample; and

sample the input signal a second time within a time window between the end of the first hold portion and an end of the first pulse to obtain a second sample indicative of a voltage level of the input signal and store said second sample; and

if the first sample and the second sample are indicative of different voltage levels, then the encoder is configured to generate, in the output signal, a second pulse, the second pulse comprising a first ramp portion in which the voltage level is changed from the first-pulse level to the second-pulse level, a first hold portion in which the second-pulse level is maintained, a second ramp portion in which the voltage level is changed from the second-pulse level to the first-pulse level and a second hold portion in which the first-pulse level is maintained, and wherein the first ramp portion and the first hold portion are provided at least over a third predetermined minimum time period and wherein the second ramp portion and the second hold portion are provided at least over a fourth predetermined minimum time period; or

if the first sample and the second sample are indicative of the same voltage levels, then the encoder is configured to maintain the voltage level in the output signal at the first-pulse level.

2. The apparatus of claim 1 , wherein the input signal is encoded with Differential Manchester Encoding.

3. The apparatus of claim 1 , wherein the encoder is configured to maintain the voltage level in the output signal at the first-pulse level in response to the first sample and the second sample being indicative of the same voltage levels, until the encoder detects a second edge in the input signal.

4. The apparatus of claim 1 , wherein the encoder is configured to detect a second edge in the input signal that follows said second pulse or that follows the maintenance of the voltage level in the output signal at the first-pulse level; and

in response to the detection of the second edge, provide said pulse generation sequence.

5. The apparatus of claim 1 , wherein the sum of the first and second predetermined minimum time periods is equal to the sum of the third and fourth predetermined minimum time periods.

6. The apparatus of claim 1 , wherein:

the first predetermined minimum time period is equal to the second predetermined minimum time period.

7. The apparatus of claim 1 , wherein:

the third predetermined minimum time period is equal to the fourth predetermined minimum time period.

8. The apparatus of claim 1 , wherein:

the sum of the first and second predetermined minimum time periods is greater than a quarter of the bit time of the input signal.

9. The apparatus of claim 1 , wherein:

the sum of the third and fourth predetermined minimum time periods is greater than a quarter of the bit time of the input signal.

10. The apparatus of claim 1 , wherein the second sample of the input signal at the second time is within a time window between half a bit time of the input signal after the detection of the first edge and the end of the first pulse.

11. The apparatus of claim 1 , wherein said network comprises an Ethernet network and said apparatus comprises part of a transceiver for coupling to said Ethernet network.

12. The apparatus of claim 11 , wherein the transceiver comprises an Ethernet 10BASE-T1S transceiver.

13. The apparatus of claim 1 , wherein the encoder comprises a first flipflop configured to detect rising edges in said input signal and a second flipflop configured to detect falling edges in said input signal, wherein in response to detection of either of a rising edge or a falling edge, one of the respective first and second flipflops is configured to provide for initiation of said pulse generation sequence and, while said pulse generation sequence is ongoing, provide a signal to the other of the first and second flipflop modules to inhibit initiation of a further pulse generation sequence.

14. The apparatus of claim 13 , wherein the pulse generation sequence is provided by a predetermined sequence of signalling output by a respective finite state machine which is configured to be triggered by a respective one of said first flipflop and said second flipflop.

15. The apparatus of claim 1 , wherein the sum of the first and second predetermined minimum time periods is equal to or less than half a bit time of the input signal.

16. The apparatus of claim 1 , wherein the sum of the third and fourth predetermined minimum time periods is equal to or less than half a bit time of the input signal.

17. The apparatus of claim 1 , wherein the sum of the first and second predetermined minimum time periods is greater than 16 ns.

18. The apparatus of claim 1 , wherein the sum of the third and fourth predetermined minimum time periods is greater than 16 ns.

19. A combination of a transceiver that includes the apparatus of claim 1 and a microcontroller, wherein the transceiver is configured to couple to a network to receive differential signalling from the network and generate an input signal comprising a difference between the parts of the differential signalling, wherein the transceiver receives the input signal and generates the output signal, wherein said microcontroller is configured to receive said output signal and includes a decoder configured to decode the output signal to provide a bitstream for an Ethernet physical layer module of the microcontroller indicative of the voltage levels in the input signal.

20. A method for encoding an input signal into an output signal, wherein the input signal is indicative of signalling from a network and comprises at least a two-level signal that comprises either a first voltage level or a second voltage level, the method comprising, by an encoder:

detecting a first edge in the input signal;

In response to the detection of the first edge providing a pulse generation sequence comprising:

generating, in the output signal, a first pulse, the first pulse comprising a first ramp portion in which the voltage level is changed from a first-pulse level to a second-pulse level, a first hold portion in which the second-pulse level is maintained, a second ramp portion in which the voltage level is changed from the second-pulse level to the first-pulse level and a second hold portion in which the first-pulse level is maintained, and wherein the first ramp portion and the first hold portion are provided at least over a first predetermined minimum time period and wherein the second ramp portion and the second hold portion are provided at least over a second predetermined minimum time period, and wherein the first pulse is provided over the first and second minimum time periods irrespective of an edge subsequent the first edge being present in the input signal; and

sampling the input signal to obtain a first sample indicative of a voltage level of the input signal to which the input signal transitions following said detection of the first edge and store said first sample; and

sampling the input signal a second time within a time window between the end of the first hold portion and an end of the first pulse to obtain a second sample indicative of a voltage level of the input signal and store said second sample; and

if the first sample and the second sample are indicative of different voltage levels, then generating, in the output signal, a second pulse, the second pulse comprising a first ramp portion in which the voltage level is changed from the first-pulse level to the second-pulse level, a first hold portion in which the second-pulse level is maintained, a second ramp portion in which the voltage level is changed from the second-pulse level to the first-pulse level and a second hold portion in which the first-pulse level is maintained, and wherein the first ramp portion and the first hold portion are provided at least over a third predetermined minimum time period and wherein the second ramp portion and the second hold portion are provided at least over a fourth predetermined minimum time period; or

if the first sample and the second sample are indicative of the same voltage levels, then maintaining the voltage level in the output signal at the first-pulse level.