HD6432633 Datasheet, PDF (1033/1453 Pages) Renesas Technology Corp – Series of Microcomputers (MCUs: microcomputer units)

23B.4 PLL Circuit
The PLL circuit has the function of multiplying the frequency of the clock from the oscillator by a
factor of 1, 2, or 4. The multiplication factor is set with the STC bits in LPWRCR. The phase of
the rising edge of the internal clock is controlled so as to match that at the EXTAL pin. When
setting the multiplication factor, ensure that the clock frequency after multiplication does not
exceed the maximum operating frequency of the chip.
When the multiplication factor of the PLL circuit is changed, the operation varies according to the
setting of the STCS bit in SCKCR.
When STCS = 0 (initial value), the setting becomes valid after a transition to software standby
mode, watch mode, or subactive mode. The transition time count is performed in accordance with
the setting of bits STS2 to STS0 in SBYCR.
[1] The initial PLL circuit multiplication factor is 1. (The upper limit for the input clock is 25
MHz. In order to use an operating frequency higher than 25 MHz a multiplication ratio of ×2
or ×4 must be employed.)
[2] A value is set in bits STS2 to STS0 to give the specified transition time.
[3] The target value is set in STC1 and STC0, and a transition is made to software standby mode,
watch mode, or subactive mode.
[4] The clock pulse generator stops and the value set in STC1 and STC0 becomes valid.
[5] Software standby mode, watch mode, or subactive mode is cleared, and a transition time is
secured in accordance with the setting in STS2 to STS0.
[6] After the set transition time has elapsed, the LSI resumes operation using the target
multiplication factor.
If a PC break is set for the SLEEP instruction that causes a transition to software standby mode in
[3], software standby mode is entered and break exception handling is executed after the
oscillation stabilization time. In this case, the instruction following the SLEEP instruction is
executed after execution of the RTE instruction.
When STCS = 1, the LSI operates on the changed multiplication factor immediately after bits
STC1 and STC0 are rewritten.
23B.5 Medium-Speed Clock Divider
The medium-speed clock divider divides the system clock to generate ø/2, ø/4, ø/8, ø/16, and ø/32.
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