UPD78F0411GA-GAM-AX Datasheet, PDF (120/564 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 5 CLOCK GENERATOR
(9) Internal high-speed oscillation trimming register (HIOTRM)
This register corrects the accuracy of the internal high-speed oscillator. The accuracy can be corrected by self-
measuring the frequency of the internal high-speed oscillator, using a subsystem clock using a crystal resonator
or using a timer with high-accuracy external clock input, such as a real-time counter.
HIOTRM can be set by an 8-bit memory manipulation instruction.
Reset signal generation sets HIOTRM to 10H.
Caution
If the temperature or VDD pin voltage is changed after accuracy correction, the frequency will
fluctuate. Also, if a value other than the initial value (10H) is set to the HIOTRM register, the
oscillation accuracy of the internal high-speed oscillation clock may exceed the MIN. and MAX.
values described in CHAPTER 27 ELECTRICAL SPECIFICATIONS (STANDARD PRODUCTS)
due to the subsequent fluctuation in the temperature or VDD voltage, or HIOTRM register
setting value. If the temperature or VDD voltage fluctuates, accuracy correction must be
executed either before frequency accuracy will be required or regularly.
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User’s Manual U18698EJ1V0UD