Syncroniser circuit

A circuit portion comprising:

• a synchroniser comprising:
• a signal input for receiving a signal clocked at a first frequency;
• and
• a signal output for outputting a synchronised signal clocked at a second frequency;
• and
• a bounce-rejection circuit portion arranged to receive a synchronised signal from the output of the synchroniser;
• the bounce-rejection circuit portion being arranged to operate on a plurality of successive samples of the synchronised signal and output an output signal;
• wherein the bounce-rejection circuit portion is arranged to:
• change the output signal from a first value to a second value if a proportion of said plurality of successive samples having said second value is determined to meet a threshold, wherein the threshold is greater than 50% of the plurality of successive samples;
• or
• otherwise, maintain the output signal at the first value.

A handshake synchroniser system for synchronising a signal at a clock domain crossing, comprising:

• a first clock domain comprising:
• a first synchroniser comprising a first signal input for receiving a signal clocked at a second frequency and a first signal output for outputting a synchronised signal clocked at a first frequency;
• and
• a second clock domain comprising:
• a second synchroniser comprising a second signal input for receiving a signal clocked at the first frequency and a second signal output for outputting a synchronised signal clocked at the second frequency;
• and
• wherein each of the first and second clock domains comprise a respective bounce-rejection circuit portion arranged to receive a respective synchronised signal from the output of their respective synchroniser;
• each bounce-rejection circuit portion being arranged to operate on a plurality of successive samples of the respective synchronised signal and output a respective output signal;
• wherein each bounce-rejection circuit portion is arranged to:
• change its output signal from a first value to a second value if a proportion of said plurality of successive samples having said second value is determined to meet a threshold, wherein the threshold is greater than 50% of the plurality of successive samples;
• or
• otherwise, maintain its output signal at the first value.