Apparatus comprises master counter circuitry to generate a master count signal in response to a clock signal; slave counter circuitry responsive to the clock signal to generate a respective slave count signal; and a synchronisation connection providing signal communication between the master counter circuitry and the slave counter circuitry; the master counter circuitry being configured to provide to the slave counter circuitry via the synchronisation connection: (i) data indicative of a count offset value and (ii) a timing signal defining a timing relationship between the clock signal and the count offset value; and the slave counter circuitry being configured, during a synchronisation operation for that slave counter circuitry, to initialise a counting operation of that slave counter circuitry in response to the data indicative of the count offset value and a timing signal provided by the master counter circuitry.