MAC7200 datasheet(948/976 Pages) FREESCALE

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Oscillator Characteristics

MAC7200 Microcontroller Family Reference Manual, Rev. 2

870

Freescale Semiconductor

XCLKS signal at the rising edge of the RESET signal. Before asserting the oscillator to the internal system

clock distribution subsystem, the quality of the oscillator output clock is checked for each start from either

power on reset (POR) or reset after a Clock Monitor Failure. tCQOUT specifies the maximum time before

switching to the internal self clock mode after POR if a proper oscillator clock output is not detected. The

quality check also determines the minimum oscillator start-up time tUPOSC. The device also features a

Crystal Monitor. A Crystal Monitor Failure is asserted if the frequency of the incoming clock signal is

below the Crystal Monitor Assert Frequency fCMFA.

NOTE

The use of overtone resonators (Ceramic or Crystal) is not recommended.

NOTE

The oscillators on the MAC71xx and MAC72xx are different designs. You

should characterize your oscillator design if you switch between the two

devices.

Table A-14. Oscillator Characteristics

Num

Rating

Symbol

Min

Typ

Max

Unit

H1a

Crystal oscillator frequency (ALC Mode)1

1. XCLKS negated (1) during reset

fOSC

2. If CLKSEL[PLLSEL] is clear then the system clock (fSYS) is equal to fOSC, otherwise it is equal to fVCO. Throughout this

document, tSYS is used to specify a unit of time equal to 1 / fSYS.

4.0

—

20 (MAC72x2)

40 (MAC72x1)

MHz

H1b

External Clock Frequency (Oscillator bypassed)3

3. XCLKS asserted (0) during reset

fOSC

0.5

—

MHz

Crystal oscillator reference duty cycle

tDUTY

—

Startup Current

IOSC

1.2

—

Supply Voltage

VDDPLL

3.0

3.3

3.6

Supply Current

IOSC

——

Oscillator start-up time (ALC Mode)

tUPOSC

—5(4)

4. fosc = 8 MHz, CLOAD = 16.5 pF, CEXTAL = 33 pF, CXTAL = 33pF.

10(5)

5. Maximum value is for extreme cases using high Q, low frequency crystals

Clock Quality check time-out

tCQOUT

0.45

—

2.5

Clock Monitor Failure Assert Frequency

fCMFA

100

200

400

KHz

External Clock Duty Cycle

—

40/60

—

H10

External Clock rise time

tEXTR

——

H11

External Clock fall time

tEXTF

——

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