Abstract: A frequency modulation circuit includes an emitter-follower connection transistor (2), having a base supplied with a modulation signal, for generating an emitter voltage which is in proportion to a modulation signal level; and an integrated mono-stable multi-vibrator (1) having an inversion trigger terminal ((A*)), a non-inversion trigger terminal (B), a resister/capacitor terminal (R.sub.X /C.sub.X), a capacitor terminal (C.sub.X), complementary output terminals (Q, (Q*)), and the like. The inversion trigger terminal ((A*)) is connected to the complementary output terminal (Q), the non-inversion trigger terminal (B) is connected to a partial voltage point of partial voltage resistors (10, 11), the capacitor/resistor terminal (R.sub.X /C.sub.X) is connected to the emitter of the transistor (2) through a resistor (3) and connected to the capacitor terminal (C.sub.

Abstract: A character pattern data holding circuit includes a through latch. In a mode other than a character display mode, a gate of the through latch is opened according to an access command from the main system by making use of a data function of the through latch so that the main system and a second memory are directly connected to each other. In this way, display control timing restrictions are not imposed on the main system and access performance is enhanced.