CHAPTER 5 CLOCK GENERATOR
115
User’s Manual U11302EJ4V0UM
5.5.1 Main system clock operations
During operation with the main system clock (when bit 5 (CLS) of the processor clock control register (PCC) is
set to 0), the following operations are carried out via PCC settings.
(a) Because the operation guaranteed instruction execution speed depends on the power supply voltage, the
minimum instruction execution time can be changed by setting bits 0 to 2 (PCC0 to PCC2) of PCC.
(b) If bit 7 (MCC) of PCC is set to 1 during operation with the main system clock, the main system clock oscillation
does not stop. When bit 4 (CSS) of 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 5-9
).
Figure 5-9. Main System Clock Stop Function (1/2)
(a) Operation when MCC is set after setting CSS during main system clock operation
(b) Operation when MCC is set during main system clock operation
MCC
CSS
CLS
Main system clock oscillation
Subsystem clock oscillation
CPU clock
MCC
CSS
CLS
Main system clock oscillation
Subsystem clock oscillation
CPU clock
“L”
“L”
Oscillation does not stop.
Содержание mPD780208 Subseries
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