MC908QY8CDWE Datasheet, PDF (153/232 Pages) Freescale Semiconductor, Inc – Addendum to MC68HC908QB8, rev. 3

Low-Power Modes
In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the
module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode.
Wait mode can also be exited by a reset (or break in emulation mode). A break interrupt during wait mode
sets the SIM break stop/wait bit, SBSW, in the break status register (BSR). If the COP disable bit, COPD,
in the configuration register is 0, then the computer operating properly module (COP) is enabled and
remains active in wait mode.
Figure 14-15 and Figure 14-16 show the timing for wait recovery.
ADDRESS BUS
$6E0B
$6E0C $00FF $00FE $00FD $00FC
DATA BUS $A6 $A6
$A6
$01
$0B
$6E
EXITSTOPWAIT
NOTE: EXITSTOPWAIT = RST pin OR CPU interrupt
Figure 14-15. Wait Recovery from Interrupt
ADDRESS BUS
$6E0B
32
CYCLES
32
CYCLES
RSTVCTH RSTVCTL
DATA BUS $A6 $A6
$A6
RST⁽¹⁾
BUSCLKX4
1. RST is only available if the RSTEN bit in the CONFIG2 register is set.
Figure 14-16. Wait Recovery from Internal Reset
14.7.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a
module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery
time has elapsed. Reset or break also causes an exit from stop mode.
The SIM disables the oscillator signals (BUSCLKX2 and BUSCLKX4) in stop mode, stopping the CPU
and peripherals. If OSCENINSTOP is set, BUSCLKX4 will remain running in STOP and can be used to
run the AWU. Stop recovery time is selectable using the SSREC bit in the configuration register 1
(CONFIG1). If SSREC is set, stop recovery is reduced from the normal delay of 4096 BUSCLKX4 cycles
down to 32. This is ideal for the internal oscillator, RC oscillator, and external oscillator options which do
not require long start-up times from stop mode.
NOTE
External crystal applications should use the full stop recovery time by
clearing the SSREC bit.
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor
151