MC9S12G Datasheet, PDF (366/1160 Pages) Freescale Semiconductor, Inc – Ignores external trigger. Performs one conversion sequence and stops.

S12 Clock, Reset and Power Management Unit (S12CPMU)
Disable PLL Lock interrupt (LOCKIE=0) and oscillator status change interrupt (OSCIE=0) before going
into Full Stop Mode.
Figure 10-32. Full Stop Mode using Oscillator Clock as Bus Clock
wakeup
CPU execution
Core
Clock
PLLCLK
STOP instruction
t_{STP_REC}
interrupt continue execution
t_lock
OSCCLK
UPOSC
PLLSEL
select OSCCLK as Core/Bus Clock by writing PLLSEL to “0”
automatically set when going into Full Stop Mode
10.4.5 External Oscillator
10.4.5.1 Enabling the External Oscillator
An example of how to use the oscillator as Bus Clock is shown in Figure 10-33.
MC9S12G Family Reference Manual, Rev.1.01
366
Freescale Semiconductor
This document is valid for the S12G96 and the S12G128 device. All information related to other devices is preliminary.