Abstract: Data transmission and reception is effected via a data transmission line between a master device, which is capable of controlling data transfer, and a slave device in synchronism with a clock signal transmitted from the master device to the slave device via a clock transmission line. A signal indicative of the presence or absence of changes in the state of the slave device is sent to a third line connecting the master device to the slave device. The master device effects transmission for the purpose of acquiring data concerning state changes on the slave device side when the signal of the third line indicates that a state change has taken place on the slave device side. The transmission load can be reduced by effecting transmission used by the master device to check data representing the state of the slave device only when necessary.

Abstract: A jitter detection device for detecting jitter of a video signal (Sv) measures a vertical period (Stf(v)) of one field (v) of the video signal (Sv) to determine, based on a vertical period signal (Stf(v)), whether the video signal (Sv) jitters or not. If the number of times (Cej) it is successively determined that the video signal (Sv) jitters is smaller than a first predetermined number of times (Tej), the video signal (Sv) is confirmed to be a jitter signal (Svj). If the number of times (Cnj) it is successively determined that the video signal (Sv) does not jitter is smaller than a second predetermined number of times (Cnj), the video signal (Sv) is confirmed to be a non-jitter signal (Svjn).