NEC 78014Y Series, User Manual

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CHAPTER 7 CLOCK GENERATOR
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7.5.1 Main system clock operations
When operated with the main system clock (with bit 5 (CLS) of the processor clock control register (PCC) set to
0), the following operations are carried out by PCC setting.
(a) Because the operation guarantee instruction execution speed depends on the power supply voltage, the
minimum instruction execution time can be changed by bits 0 to 2 (PCC0 to PCC2) of the PCC.
(b) If bit 7 (MCC) of the PCC is set to 1 when operated with the main system clock, the main system clock
oscillation does not stop. When bit 4 (CSS) of the PCC is set to 1 and the operation is switched to subsystem
clock operation (CLS = 1) after that, the main system clock oscillation stops (see Figure 7-7).
Figure 7-7. Main System Clock Stop Function (1/2)
(a) Operation when MCC is set after setting CSS with main system clock operation
MCC
CSS
CLS
Main System Clock
Oscillation
Subsystem Clock
Oscillation
CPU Clock