MAC7200 datasheet(523/976 Pages) FREESCALE

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External Signal Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

445

24.2.1

VDDPLL, VSSPLL

These pins provides operating voltage (VDDPLL) and ground (VSSPLL) for the OSC_ALC_HIP7A

circuitry. This allows the supply voltage to the OSC_ALC_HIP7A to be independently bypassed.

24.2.2

EXTAL, XTAL

These pins provide the interface for either a crystal or a CMOS compatible clock to control the internal

clock generator circuitry. EXTAL is the external clock input or the input to the crystal oscillator amplifier.

XTAL is the output of the crystal oscillator amplifier. The MCU internal system clock is derived from the

EXTAL input frequency.

NOTE

Freescale recommends an evaluation of the application board and chosen

resonator or crystal by the resonator or crystal supplier.

NOTE

Loop controlled circuit is not suited for overtone resonators and crystals.

Figure 24-2. ALC Oscillator Connections (XCLKS=1)

Figure 24-3. External Clock Connections (XCLKS=0)

24.2.3

XCLKS (eXternal CLocK Select)

The XCLKS is an active low input signal which controls whether a crystal in combination with the internal

loop controlled oscillator is used or whether external clock circuitry is used. The XCLKS signal is sampled

during reset with the rising edge of RESET. Table 24-1 lists the state coding of the sampled XCLKS signal.

MCU

EXTAL

XTAL

VSSPLL

Crystal or

ceramic resonator

MCU

EXTAL

XTAL

CMOS-COMPATIBLE

EXTERNAL OSCILLATOR

(VDDPLL-Level)

VSSPLL

MAC7200 Datasheet(PDF) 523 Page - Freescale Semiconductor, Inc