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4.4.7 Programming notes
(1) When the high speed CPU operation is not necessary, you should operate the peripheral circuits accord-
ing to the setting outline indicate below.
• CPU operating clock:
• OSC3 oscillation circuit: Off
(When the OSC3 clock is not necessary for some peripheral circuits.)
(2) Since 1 msec to several tens of msec are necessary for the oscillation to stabilize after turning the OSC3
oscillation circuit on. Consequently, you should switch the CPU operating clock (OSC1 → OSC3) after
allowing for a sufficient waiting time once the OSC3 oscillation goes on. (The oscillation start time will
vary somewhat depending on the oscillator and on the externally attached parts. Refer to the oscillation
start time example indicated in Chapter 7, "Electrical Characteristics".)
(3) When switching the clock from OSC3 to OSC1, be sure to switch OSC3 oscillation off with separate
instructions. Using a single instruction to process simultaneously can cause a malfunction of the CPU.
(4) The S1C63616 supports the SLEEP function and both the OSC1 and OSC3 oscillation circuits stop oscil-
lating when the CPU enters SLEEP mode. To prevent the CPU from a malfunction when it resumes
operating from SLEEP mode, switch the CPU clock to OSC1 before placing the CPU into SLEEP mode.
OSC1
SIC63616-(Rev. 1.0) NO. P43
3240-0412
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