MC68HC912DG128 Datasheet, PDF (171/452 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Clock Functions
Limp-Home and Fast STOP Recovery modes
interrupt request is set to indicate a return to normal operation using
EXTALi clock.
11.6.10 Pseudo-STOP exit in Limp Home mode without Delay (Fast Stop Recovery)
(NOLHM=0, CME=X, DLY=0)
If Pseudo-STOP is exited with the NOLHM bit set to 0 and the DLY bit is
cleared then the exit from Pseudo-STOP is accomplished without delay
as in Fast STOP recovery.
CAUTION:
Where Pseudo-STOP recovers using the Limp Home Clock the VCO -
which has been held in STOP - must be restarted in order to supply the
limp home frequency. This restart, which occurs at a high frequency and
ramps toward the limp home frequency, is almost immediately supplied
to the CPU before it may have reached the steady state frequency. It is
possible that the initial clock frequency may be high enough to cause the
CPU to function incorrectly with a resultant risk of code runaway.
11.6.11 Pseudo-STOP exit without Limp Home mode, clock monitor enabled
(NOLHM=1, CME=1, DLY=X)
If the NOLHM bit is set and the CME (or FCME) bits are set, a clock
monitor failure is detected when a STOP instruction is executed and the
MCU resets via the clock monitor reset vector.
11.6.12 Pseudo-STOP exit without Limp Home mode, clock monitor disabled
(NOLHM=1, CME=0, DLY=1)
If NOLHM is set to 1 and the CME and FCME bits are cleared, the limp
home clock is not used. In this mode, crystal activity is the only method
by which the device may recover from Pseudo-STOP. The device will
start execution with the EXTALi clock following 4096 XCLK cycles.
MC68HC912DG128 — Rev 3.0
MOTOROLA
Clock Functions
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Technical Data
171