Datasheet

Section 5 Clock Pulse Generators
Rev. 1.50 Sep. 18, 2007 Page 77 of 584
REJ09B0240-0150
Bit Bit Name
Initial
Value R/W Description
1  1  Reserved
This bit is always read as 1.
0 CKSTA 0 R LSI Operating Clock Status
0: This LSI operates on on-chip oscillator clock.
1: This LSI operates on external clock.
5.3 System Clock Oscillator
5.3.1 State Transition of System Clock
The system clock of this LSI is generated from the on-chip oscillator clock after a reset. System
clock sources can be switched from the on-chip oscillator clock to the external clock and vice
versa by the user software.
Figure 5.2 shows the state transition of the system clock.
LSI operates on on-chip oscillator clock
On-chip oscillator: Operated
External oscillator: Halted
Switching to
external clock
On-chip oscillator: Halted
External oscillator: Operated
On-chip oscillator: Operated
External oscillator: Operated
On-chip oscillator halted
On-chip oscillator operated
LSI operates on external clock
Reset release
Reset state
On-chip oscillator: Operated
External oscillator: Halted (I/O pin)
Switching to
on-chip oscillator clock
Reset cleared
Figure 5.2 State Transition of System Clock