CHAPTER 7 CLOCK GENERATOR (μPD789860 SUBSERIES)User’s Manual U14826EJ5V0UD747.5 Clock Generator OperationThe clock generator generates the following clocks and controls the operation modes of the CPU, such as standbymode:• System clock fX• CPU clock fCPU• Clock to peripheral hardwareThe operation of the clock generator is determined by the processor clock control register (PCC) as follows:(a) The slow mode (1.6μs: at 5.0 MHz operation) of the system clock is selected when the RESET signal isgenerated (PCC = 02H). While a low level is input to the RESET pin, oscillation of the system clock isstopped.(b) Two types of minimum instruction execution time (fCPU) (0.4μs, 1.6μs: at 5.0 MHz operation) can be selectedby setting PCC.(c) Two standby modes, STOP and HALT, can be used.(d) The clock for the peripheral hardware is generated by dividing the frequency of the system clock. Therefore,the peripheral hardware stops when the system clock stops (except for an external input clock).
