SH7751 Datasheet, PDF (369/1224 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

10. Clock Oscillation Circuits
The function of each of the CPG blocks is described below.
PLL Circuit 1: PLL circuit 1 has a function for multiplying the clock frequency from the EXTAL
pin or crystal oscillation circuit by 6 (SH7751 and SH7751R) or 12 (SH7751R). Starting and
stopping is controlled by a frequency control register setting. Control is performed so that the
internal clock rising edge phase matches the input clock rising edge phase.
PLL Circuit 2: PLL circuit 2, according to the output clock feedback from the CKIO pin,
coordinates the phases of the bus clock and the CKIO pin output clock. Starting and stopping is
controlled by a frequency control register setting.
Crystal Oscillation Circuit: This is the oscillator circuit used when a crystal resonator is
connected to the XTAL and EXTAL pins. Use of the crystal oscillation circuit can be selected
with the MD8 pin.
Frequency Divider 1 (SH7751R only): Frequency divider 1 has a function for adjusting the clock
waveform duty to 50% by halving the input clock frequency when clock input from the EXTAL
pin is supplied internally without using PLL circuit 1.
Frequency Divider 2: Frequency divider 2 generates the CPU clock (Ick), bus clock (Bck), and
peripheral module clock (Pck). The division ratio is set in the frequency control register.
Clock Frequency Control Circuit: The clock frequency control circuit controls the clock
frequency by means of the MD pins and frequency control register.
Standby Control Circuit: The standby control circuit controls the state of the on-chip oscillation
circuits and other modules when the clock is switched and in sleep and standby modes.
Frequency Control Register (FRQCR): The frequency control register contains control bits for
clock output from the CKIO pin, PLL circuit 1 and 2 on/off control, and the CPU clock, bus clock,
and peripheral module clock frequency division ratios.
Standby Control Register (STBCR): The standby control register contains power save mode
control bits. For further information on the standby control register, see section 9, Power-Down
Modes.
Standby Control Register 2 (STBCR2): Standby control register 2 contains a power save mode
control bit. For further information on standby control register 2, see section 9, Power-Down
Modes.
Rev.4.00 Oct. 10, 2008 Page 271 of 1122
REJ09B0370-0400