Datasheet

Clock Functions
Limp-Home and Fast STOP Recovery modes
MC68HC912D60A — Rev. 3.1 Technical Data
Freescale Semiconductor Clock Functions 155
..
Table 11-1. Summary of STOP Mode Exit Conditions
Mode Conditions Summary
STOP exit without Limp Home
mode,
clock monitor disabled
NOLHM=1
CME=0
DLY=X
Oscillator must be stable within 4096 XCLK cycles. XCLK
can be modified by SLOW divider register.
Use of DLY=0 only recommended with external clock.
Executing the STOP instruction
without Limp Home mode,
clock monitor enabled
NOLHM=1
CME=1
DLY=X
When a STOP instruction is executed the MCU resets via
the clock monitor reset vector.
STOP exit in Limp Home mode
with Delay
NOLHM=0
CME=X
DLY=1
Oscillator must be stable within 4096
f
VCOMIN
cycles or there is a possibility of code runaway as
the clock monitor circuit can be misled by EXTALi clock
into reporting a good signal before it has fully stabilised
STOP exit in Limp Home mode
without Delay (Fast Stop
Recovery)
NOLHM=0
CME=X
DLY=0
This mode is only recommended for use with an external
clock source.
Table 11-2. Summary of Pseudo STOP Mode Exit Conditions
Mode Conditions Summary
Pseudo-STOP exit in Limp Home
mode with Delay
NOLHM=0
CME=X
DLY=1
CPU exits stop in limp home mode and oscillator running. If
the oscillator fails during pseudo-STOP and then recovers
there is a possibility of code runaway as the clock monitor
circuit can be misled by EXTALi clock into reporting a
good signal before it has fully stabilised
Pseudo-STOP exit
in Limp Home mode without
Delay (Fast Stop Recovery)
NOLHM=0
CME=X
DLY=0
This mode is not recommended as it is possible that the
initial VCO clock frequency may be high enough to cause
code runaway.
Pseudo-STOP exit without Limp
Home mode, clock monitor
enabled
NOLHM=1
CME=1
DLY=X
When a STOP instruction is executed the MCU resets via
the clock monitor reset vector.
Pseudo-STOP exit without Limp
Home mode, clock monitor
disabled, with Delay
NOLHM=1
CME=0
DLY=1
Oscillator starts operation following 4096 XCLK cycles
(actual controlled by SLOW mode divider).
Pseudo-STOP exit without Limp
Home mode, clock monitor
disabled, without Delay
NOLHM=1
CME=0
DLY=0
This mode is only recommended for use with an external
clock source.