JPS6482864A - Control circuit for video memory - Google Patents

Abstract

PURPOSE:To prevent the disorder of an image from being generated on a screen at the time of switching by stopping write to a memory beforehand, when a video signal written in the memory is switched, and thereafter, reading out repeatedly the same contents for a prescribed period. CONSTITUTION:When a picture-in-picture processing is being executed, and a video signal from a tuner 1 is selected for slave picture plane use, only a channel switching signal from a timing control circuit 19 becomes effective. In this state, a still picture instructing signal S rises at a timing of a vertical synchronizing signal of the next slave screen in which a channel switching signal CH from a channel selection switching instruction circuit 16 or a sequential channel selection means 17 has been generated. Accordingly, as for a memory 9, only a read-out operation is executed. Subsequently, at a timing of a second vertical synchronizing signal, a channel switching signal Tu is outputted, and a channel selection channel is changed. In this case, a video signal of an old channel is read out repeatedly, therefore, no disorder is generated on a screen of a TV receiver.