Motorola MCU 68HC912D60 Manual de usuario descargar pdf (Pagina 5)

68HC912D60MSE4 Rev 2 5

March 14, 2001

BRCLRRTIFLG,#RTIF,RTIFClr; RTIF flag is already clear

LDAB#RTIF; if it’s set, clear the flag.

STABRTIFLG

RTIFClr:BRCLRRTIFLG,#RTIF,*; wait until the RTIFLG is set.

NOP

STOP ; enter stop mode

2. If you are driving a clock in (not using the OSC) then you could set DLY=0.

3. Pseudo-STOP and DLY=0 could be used. The oscillator will be kept alive

during STOP at the expense of power consumption but no recovery delay is

needed. Set the PSTP bit and clear DLY bit prior to going to STOP.

4. Limp Home and DLY=0 could be used. The part comes out of STOP in limp

home mode while the crystal recovers. If a known frequency is not a

requirement, this workaround avoids having the crystal alive in STOP mode.

Clear the NOLHM and DLY bits prior to going to STOP.

CGM: OSCILLATOR START-UP WITH 8MHZ AND 16MHZ CRYSTALS AND

RESONATORS AR536

It is possible that oscillator start up will fail with high frequency crystals and

resonators under specific environmental conditions where moisture forms on the

pins of the MCU, creating a leakage path to Vss or Vdd.

Typical conditions for failure are the following: 8Mhz or higher frequency crystal or

resonator and leakage on the EXTAL pin to Vss corresponding to an impedance of

8M ohms.

No failures have been observed with moisture affecting oscillator start-up with

resonators or crystals at or below 4Mhz frequency. Once started, the oscillation is

not affected by moisture. The issue is only related to oscillator start-up.

Work-

around

Conformal coating (water repellent or sealant) is required across the oscillator

components and oscillator pins of the MCU where there is a possibility of the

leakage paths described above.

The most critical area is around the EXTAL pin of the MCU where it is more likely

to have a small spacing between EXTAL exposed tracks and low voltage sources.

In particular the EXTAL and RESET pins are next to each other. At Power-on, the

RESET pin is held to Vss in most systems and may be the most likely leakage path

if condensation forms on the MCU pins.

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Motorola MCU 68HC912D60 Manual de usuario Pagina 5