
CHAPTER 6 CLOCK GENERATION FUNCTION
User’s Manual U17790EJ2V0UD
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(1) Main clock oscillator
The main resonator oscillates the following frequencies (fX).
In clock-through mode
fX = 2.5 to 10 MHz
In PLL mode
fX = 2.5 to 5 MHz (
×4)
fX = 2.5 to 4 MHz (
×8)
(2) Subclock oscillator
The sub-resonator oscillates a frequency of 32.768 kHz (fXT).
(3) Main clock oscillator stop control
This circuit generates a control signal that stops oscillation of the main clock oscillator.
Oscillation of the main clock oscillator is stopped in the STOP mode or when the PCC.MCK bit = 1 (valid only
when the PCC.CLS bit = 1).
(4) Internal oscillator
Oscillates a frequency (fR) of 220 kHz (TYP.).
(5) Prescaler 1
This prescaler generates the clock (fXX to fXX/1,024) to be supplied to the following on-chip peripheral functions:
TMP0 to TMP8, TMQ0, TMM0, CSIB0 to CSIB5, UARTA0 to UARTA3, I
2C00 to I2C02, ADC, WDT2, CAN0Note 1,
CAN1
Note 2, and IEBus
Notes 1. CAN controller version only
2. CAN controller (2-channel) version only
(6) Prescaler 2
This circuit divides the main clock (fXX).
The clock generated by prescaler 2 (fXX to fXX/32) is supplied to the selector that generates the CPU clock
(fCPU) and internal system clock (fCLK).
fCLK is the clock supplied to the INTC, ROM correction, ROM, and RAM blocks, and can be output from the
CLKOUT pin.
(7) Prescaler 3
This circuit divides the clock generated by the main clock oscillator (fX) to a specific frequency (32.768 kHz)
and supplies that clock to the watch timer block.
For details, see CHAPTER 10 WATCH TIMER FUNCTIONS.
(8) PLL
This circuit multiplies the clock generated by the main clock oscillator (fX) by 4 or 8.
It operates in two modes: clock-through mode in which fX is output as is, and PLL mode in which a multiplied
clock is output. These modes can be selected by using the PLLCTL.SELPLL bit.
Whether the clock is multiplied by 4 or 8 is selected by the CKC.CKDIV0 bit, and PLL is started or stopped by
the PLLCTL.PLLON bit.