mc68hc08qa24 Freescale Semiconductor, Inc, mc68hc08qa24 Datasheet - Page 146

• Manufacturer Part Number: mc68hc08qa24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
10.6.4 Status Flag Protection in Break Mode
10.7 Low-Power Modes
10.7.1 Wait Mode
Technical Data
144
The SIM controls whether status flags contained in other modules can
be cleared during break mode. The user can select to protect flags from
being cleared by properly initializing the break clear flag enable bit
(BCFE) in the SIM break flag control register (SBFCR). (See
Break Flag Control
Protecting flags in break mode ensures that set flags will not be cleared
while in break mode. This protection allows registers to be freely read
and written during break mode without losing status flag information.
Setting the BCFE bit enables the clearing mechanisms. Once cleared in
break mode, a flag remains cleared even when break mode is exited.
Status flags with a 2-step clearing mechanism — for example, a read of
one register followed by the read or write of another — are protected,
even when the first step is accomplished prior to entering break mode.
Upon leaving break mode, execution of the second step will clear the flag
as usual.
Executing the WAIT or STOP instruction puts the MCU in a low power-
consumption mode for standby situations. The SIM holds the CPU in a
non-clocked state. The operation of each of these modes is described in
this section. Both STOP and WAIT clear the interrupt mask (I) in the
condition code register, allowing interrupts to occur.
In wait mode, the CPU clocks are inactive while one set of peripheral
clocks continues to run.
entry.
A module that is active during wait mode can wake up the CPU with an
interrupt if the interrupt is enabled. Stacking for the interrupt begins one
cycle after the WAIT instruction during which the interrupt occurred.
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.
System Integration Module (SIM)
Register.)
Figure 10-12
shows the timing for wait mode
Freescale Semiconductor
MC68HC08QA24
10.8.3 SIM