Datasheet

Section 5 Clock Pulse Generators
Rev. 3.00 Sep. 14, 2006 Page 80 of 408
REJ09B0105-0300
5.4 Trimming of On-chip Oscillator Frequency
Users can trim the on-chip oscillator frequency, supplying the external reference pulses with the
input capture function in internal timer W. An example of trimming flow and a timing chart are
shown in figures 5.7 and 5.8, respectively. Because RCTRMDR is initialized by a reset, when
users have trimmed the oscillators, some operations after a reset are necessary, such as trimming it
again or saving the trimming value in an external device for later reloading.
Yes
No
Note: * Comparing the difference between the measured frequency and the desired frequency,
individual bits of RCTRMDR are decided from the MSB bit by bit.
Start
Setting timer W
GRA: Input capture
GRC: Buffer of GRA
Set RCTRMD to H'00
Input reference pulses to
pin P81/FTIOA
Capture 1
Capture 2
Frequency calculation
Within
desired frequency
range?
End
Modify RCTRMDR*
Figure 5.7 Example of Trimming Flow for On-chip Oscillator Frequency