Datasheet

Section 23 Clock Pulse Generator
Rev.7.00 Mar. 18, 2009 page 961 of 1136
REJ09B0109-0700
23.3 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 STC1 and the STC0 bits in PLLCR.
The phase of the rising edge of the internal clock is controlled so as to match that of the rising
edge of the EXTAL pin.
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, the setting becomes valid after a transition to software standby mode. The
transition time count is performed in accordance with the setting of bits STS3 to STS0 in SBYCR.
For details on SBYCR, refer to section 24.1.1, Standby Control Register (SBYCR).
1. The initial PLL circuit multiplication factor is 1.
2. A value is set in bits STS3 to STS0 to give the specified transition time.
3. The target value is set in bits STC1 and STC0, and a transition is made to software standby
mode.
4. The clock pulse generator stops and the value set in STC1 and STC0 becomes valid.
5. Software standby mode is cleared, and a transition time is secured in accordance with the
setting in STS3 to STS0.
6. After the set transition time has elapsed, this LSI resumes operation using the target
multiplication factor.
When STCS = 1, this LSI operates using the new multiplication factor immediately after bits
STC1 and STC0 are rewritten.
23.4 Frequency Divider
The frequency divider divides the PLL output clock to generate a 1/2, 1/4, or 1/8 clock.