Freescale Semiconductor MCF51QE128RM manual Icsirclk

Chapter 1 Device Overview

XTAL	EXTAL				TPM1CLK	TPM2CLK	TPM3CLK
XOSC	OSCOUT		RTC	COP	TPM1	TPM2	TPM3
	ICSIRCLK
	ICSERCLK
	1KHz LPO	LPOCLK
	ICSFFCLK	⎟2	SYNC*		FFCLK*
ICS
	ICSOUT	⎟2	BUSCLK
	ICSLCLK

SCI1 &	SPI1 &	ACMP1 &
SCI2	SPI2	ACMP2

CPU &

RGPIO

Debug

RAM

BDC

IIC1 &

IIC2

PMC

ADC

FLASH

GPIO

INTC

*The fixed frequency clock (FFCLK) is internally synchronized to the bus clock and must not exceed one half of the bus clock frequency.

ADC has min and max	Flash has frequency
frequency requirements.	requirements for program
See the ADC chapter	and erase operation.
and the MCF51QE128	See the MCF51QE128
Data Sheet for details.	Data Sheet for details.

Figure 1-3. System Clock Distribution Diagram

•OSCOUT — This is the direct output of the external oscillator module and can be selected as the real-time counter clock source. See Chapter 14, “Real-Time Counter (S08RTCV1),” for more information.

•ICSERCLK — This is the external reference clock and can be selected as the real-time counter clock source or the alternate clock for the ADC module. Section 11.4.7, “External Reference Clock,” explains the ICSERCLK in more detail. See Chapter 11, “Analog-to-Digital Converter (S08ADC12V1),” for more information regarding the use of ICSERCLK with this module.

•ICSIRCLK — This is the internal reference clock and can be selected as the real-time counter clock source. Section 11.4.6, “Internal Reference Clock,” explains the ICSIRCLK in more detail. See Chapter 14, “Real-Time Counter (S08RTCV1),” for more information regarding the use of

ICSIRCLK.

•ICSFFCLK — This generates the fixed frequency clock (FFCLK) after being synchronized to the bus clock. It can be selected as clock source for the TPM modules. The frequency of the ICSFFCLK is determined by the settings of the ICS. See Section 11.4.8, “Fixed Frequency Clock,” for details.

•LPOCLK — This clock is generated from an internal low-power oscillator that is completely independent of the ICS module. The LPOCLK can be selected as the clock source to the RTC or COP modules. See Chapter 14, “Real-Time Counter (S08RTCV1),” and Section 5.3.1, “Computer Operating Properly (COP) Watchdog,” for details on using the LPOCLK with these modules.

•TPMxCLK — TPMxCLKs are optional external clock sources for the TPM modules. The TPMxCLK must be limited to 1/4 the frequency of the bus clock for synchronization. See Section 16.2.1, “External TPM Clock Sources,” for more details.

MCF51QE128 MCU Series Reference Manual, Rev. 3

28 Freescale Semiconductor

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