Patent ID: 7194648

Claim:
A method for time synchronisation of at least two clocks contained in a multiprocessor system, wherein a first clock having a predetermined clock rate generates consecutive respective time-stamps indicating the time and at least one second clock, which has an adjustable clock rate, is synchronised with the first clock at certain intervals, comprising: a) recording, at predetermined time intervals, the relative temporal position of flanks of the first clock and of the second clock representing the transition between two consecutive time-stamps; b) determining, from the change in the relative temporal position of the transition flanks of the first clock and of the second clock, a correction factor representing the time deviation between the first clock and the second clock; c) readjusting, using the correction factor representing the time deviation between the first clock and the second clock, the clock rate of the second clock, wherein the readjustment is a diminution of the time deviation between the first clock and the second clock; and d) repeating steps a) to c), wherein the change in the temporal position of the transition flank of the first clock and of the second clock is recorded by a two-stage flank search, by the time-stamp of the clock in question being read out once before an assumed transition flank between two consecutive time-stamps and once after an assumed transition flank between two consecutive time-stamps and by the time-stamp obtained in each instance being compared with the time-stamp expected for the time of read-out and by this process being continued, wherein i) a concordance both of the time-stamp obtained in the case of read-out before the assumed transition flank with the expected time-stamp and of the time-stamp obtained in the case of read-out after the assumed transition flank with the expected time-stamp is appraised with respect to a correct position of the assumed transition flank, ii) a concordance of the time-stamp obtained in the case of read-out before the assumed transition flank with the expected time-stamp and a concordance of the time-stamp obtained in the case of read-out after the assumed transition flank, but with an earlier time-stamp than that expected, is appraised with respect to a belated position of the assumed transition flank, and iii) a concordance of the time-stamp obtained in the case of read-out after the assumed transition flank with the expected time-stamp and a concordance of the time-stamp obtained in the case of read-out before the assumed transition flank, but with a later time-stamp than that expected, is appraised with respect to a premature position of the assumed transition flank.