mitsubishi - Al Kossow's Bitsavers

MITSUBISHI MICROCOMPUTERSMS0740-XXXS PSINGLE-CHIP a-BIT CMOS MICROCOMPUTERClock Generator CircuitThe clock generator circuit is built-in, as shown in Fig. 11.When the STP instruction is executed, oscillation is stoppedwith the internal clock if> in the high-level. Furthermore, FF 16is set in prescaler X and 01 16 in timer X, and the output,one-sixteenth of the oscillator output, is forcibly connectedto the prescaler X input. This connection is released when,as mentioned in the timer section, timer X overflows orwhen resetting is accomplished. Oscillation re-starts whenan interrupt is acknowledged but the internal clock if> ,remains high until timer X: overflows. Only when timer Xoverflows is the internal clock if> supplied. This is becausetime is required for the oscillation to rise when a ceramicresonator or similar part is employed.When the FST instruction is executed, ,SWase closes andwhen the SLW instruction is executed, it opens. These instructionsare used when RC oscillation is emploied andthe oscillation frequency is changed. SWase is closed duringresetting.IIInterrupt requestInterrupt disable flag ISoSTP instruction -----I ROverflowSW{>CE=O~-'--~Intemal clock ¢>RESETRt----STP instructionFlg.l1Block diagram of clock generator circuit• MITSUBISHI"ELECTRIC3-13