S12SCIV2SLASHD datasheet(108/130 Pages) FREESCALE

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MC9S12H256 Device User Guide — V01.18

A.4.1.4 Stop Recovery

Out of STOP the controller can be woken up by an external interrupt. A clock quality check as after POR

is performed before releasing the clocks to the system.

A.4.1.5 Pseudo Stop and Wait Recovery

The recovery from Pseudo STOP and Wait are essentially the same since the oscillator was not stopped in

both modes. The controller can be woken up by internal or external interrupts. After twrs the CPU starts

fetching the interrupt vector.

A.4.2 Oscillator

The device features an internal Colpitts oscillator. By asserting the XCLKS input during reset this

oscillator can be bypassed allowing the input of a square wave. Before asserting the oscillator to the

internal system clocks the quality of the oscillation is checked for each start from either power-on, STOP

or oscillator fail. tCQOUT specifies the maximum time before switching to the internal self clock mode after

POR or STOP if a proper oscillation is not detected. The quality check also determines the minimum

oscillator start-up time tUPOSC. The device also features a clock monitor. A Clock Monitor Failure is

asserted if the frequency of the incoming clock signal is below the Assert Frequency fCMFA.

Table A-14 Oscillator Characteristics

Conditions are shown in Table A-4 unless otherwise noted

Num C

Rating

Symbol

Min

Typ

Max

Unit

C Crystal oscillator range

fOSC

0.5

MHz

P Startup Current

iOSC

100

µA

D Oscillator start-up time from POR or STOP

nUPOSC

4100

cycOSC

C Oscillator start-up time

tUPOSC

NOTES:

1. fosc = 4MHz, C = 22pF.

1002

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

D Clock Quality check time-out

tCQOUT

0.45

2.5

P Clock Monitor Failure Assert Frequency

fCMFA

100

200

KHz

7P External square wave input frequency3

fEXT

0.5

MHz

D External square wave pulse width low

tEXTL

D External square wave pulse width high

tEXTH

D External square wave rise time

tEXTR

1ns

D External square wave fall time

tEXTF

1ns

D Input Capacitance EXTAL pin

CIN

9pF

D Input Capacitance XTAL pin

CIN

DC Operating Bias in Colpitts Conﬁguration on

EXTAL Pin

VDCBIAS

1.1

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