
Section 4 Clock Pulse Generator (CPG)
R01UH0025EJ0300 Rev. 3.00
Page 79 of 1336
Sep 24, 2010
SH7261 Group
The clock pulse generator blocks function as follows:
(1)
PLL Circuit 1
PLL circuit 1 multiplies the input clock frequency from the CKIO pin by 1, 2, 3, 4, 6, or 8. The
multiplication rate is set by the frequency control register. When this is done, the phase of the
rising edge of the bus clock is controlled so that it will agree with the phase of the rising edge of
the CKIO pin.
(2)
PLL Circuit 2
PLL circuit 2 multiplies the input clock frequency from the crystal oscillator or EXTAL pin by 2
or 4. The multiplication rate is fixed according to the clock operating mode. The clock operating
mode is specified by the MD_CLK1 and MD_CLK0 pins. For details on the clock operating
mode, see table 4.2.
Note that the settings of these pins cannot be changed during operation. If changed, the operation
of this LSI cannot be guaranteed.
(3)
Crystal Oscillator
The crystal oscillator is an oscillation circuit in which a crystal resonator is connected to the
XTAL pin or EXTAL pin. This can be used according to the clock operating mode.
(4)
Divider
Divider generates a clock signal at the operating frequency used by the CPU or peripheral clock.
The operating frequency can be 1, 1/2, 1/3, 1/4, 1/6, 1/8, or 1/12 times the output frequency of
PLL circuit 1, as long as it stays at or above the clock frequency of the CKIO pin. The division
ratio is set in the frequency control register (FRQCR).
(5)
Clock Frequency Control Circuit
The clock frequency control circuit controls the clock frequency using the MD_CLK1 and
MD_CLK0 pins and the frequency control register (FRQCR).
(6)
Standby Control Circuit
The standby control circuit controls the states of the clock pulse generator and other modules
during clock switching, or in sleep, software, and deep standby mode.