Datasheet

Section 5 Clock Pulse Generators
Rev. 1.50 Sep. 18, 2007 Page 82 of 584
REJ09B0240-0150
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 timer RC or timer RD. An example of trimming flow using timer RC 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.
Ye s
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 RC
GRA: Input capture
GRC: Buffer of GRA
Set RCTRMD to H'00
Input reference pulses to
pin PH4/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