Motorola MC9S12DT128B, MC9S12DB128B manual A.5.2 Oscillator, A.5.1.5 Pseudo Stop and Wait Recovery

MC9S12DT128B Device User Guide — V01.07

A.5.1.5 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.5.2 Oscillator

The device features an internal Colpitts and Pierce oscillator. The selection of Colpitts oscillator or Pierce oscillator/external clock depends on the XCLKS signal which is sampled during reset.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-15 Oscillator Characteristics

Conditions are shown in Table A-4unless otherwise noted

Num	C	Rating	Symbol	Min	Typ	Max	Unit
1a	C	Crystal oscillator range (Colpitts)	fOSC	0.5		16	MHz
1b	C	Crystal oscillator range (Pierce) 1	fOSC	0.5		40	MHz
2	P	Startup Current	iOSC	100			μA
3	C	Oscillator start-up time (Colpitts)	tUPOSC		82	1003	ms
4	D	Clock Quality check time-out	tCQOUT	0.45		2.5	s
5	P	Clock Monitor Failure Assert Frequency	fCMFA	50	100	200	KHz
6	P	External square wave input frequency 4	fEXT	0.5		50	MHz
7	D	External square wave pulse width low	tEXTL	9.5			ns
8	D	External square wave pulse width high	tEXTH	9.5			ns
9	D	External square wave rise time	tEXTR			1	ns
10	D	External square wave fall time	tEXTF			1	ns
11	D	Input Capacitance (EXTAL, XTAL pins)	CIN		7		pF
12	C	DC Operating Bias in Colpitts Configuration on	VDCBIAS		1.1		V
		EXTAL Pin
NOTES:

1.Depending on the crystal a damping series resistor might be necessary

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

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

4.XCLKS =0 during reset

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