Section 4 Clock Pulse Generator (CPG)
Rev. 3.00 Sep. 27, 2007 Page 57 of 758
REJ09B0243-0300
The clock pulse generator blocks function as follows:
PLL Circuit:
The PLL circuit multiples the clock frequency input from the crystal oscillator or
the EXTAL pin by 8. The multiplication ratio is fixed at
×
8.
Crystal Oscillator:
The crystal oscillator is an oscillator circuit when a crystal resonator is
connected to the XTAL and EXTAL pins.
Divider:
The divider generates clocks with the frequencies to be used by the internal clock (I
φ
),
bus clock (B
φ
), peripheral clock (P
φ
), and MTU2 clock (MP
φ
).
The frequencies can be selected from 1/2, 1/4 (initial value), and 1/8 times the frequency output
from the PLL circuit. The division ratio should be specified in the frequency control register
(FRQCR).
Oscillation Stop Detection Circuit:
This circuit detects an abnormal condition in the crystal
oscillator.
Clock Frequency Control Circuit:
The clock frequency control circuit controls the clock
frequency according to the setting in the frequency control register (FRQCR).
Standby Control Circuit:
The standby control circuit controls the state of the on-chip oscillator
circuit and other modules in sleep or standby mode.
Frequency Control Register (FRQCR):
The frequency control register (FRQCR) has control
bits for the frequency division ratios of the internal clock (I
φ
), bus clock (B
φ
), peripheral clock
(P
φ
), and MTU2 clock (MP
φ
).
Oscillation Stop Detection Control Register (OSCCR):
The oscillation stop detection control
register (OSCCR) has an oscillation stop detection flag and a bit for selecting flag status output
through an external pin.
Standby Control Registers 1 to 6 (STBCR1 to STBCR6):
The standby control register
(STBCR) has bits for controlling the power-down modes. For details, see section 19, Power-Down
Modes.
Содержание SH7124 R5F7124
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