MC908KX2MDWE Datasheet, PDF (153/210 Pages) Freescale Semiconductor, Inc – High-performance M68HC08 architecture, Fully upward-compatible object code with M6805, M146805, and M68HC05 Families

TBM Interrupt Rate
14.5 TBM Interrupt Rate
The interrupt rate is determined by the equation:
t_TBMRATE
=
-----------1-------------
f_TBMRATE
=
-D----i--v----i-d----e----r
f_TBMCLK
where:
f_TBMCLK = Frequency supplied from the internal clock generator (ICG) module
Divider = Divider value as determined by TBR2–TBR0 settings. See Table 14-1.
As an example, a clock source of 4.9152 MHz and the TBR2–TBR0 set to {011}, the divider tap is 128
and the interrupt rate calculates to 128/4.9152 x 10⁶ = 26 µs.
Table 14-1. Timebase Divider Selection
TBR2
0
0
0
0
1
1
1
1
TBR1
0
0
1
1
0
0
1
1
TBR0
0
1
0
1
0
1
0
1
Divider Tap
32768
8192
2048
128
64
32
16
8
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
14.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
14.6.1 Wait Mode
The timebase module remains active after execution of the WAIT instruction. In wait mode the timebase
register is not accessible by the CPU.
If the timebase functions are not required during wait mode, reduce the power consumption by stopping
the timebase before executing the WAIT instruction.
14.6.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the internal clock
generator has been enabled to operate during stop mode through the OSCENINSTOP bit in the
configuration register. The timebase module can be used in this mode to generate a periodic wake up
from stop mode.
If the internal clock generator has not been enabled to operate in stop mode, the timebase module will
not be active during stop mode. In stop mode, the timebase register is not accessible by the CPU.
If the timebase functions are not required during stop mode, reduce power consumption by disabling the
timebase module before executing the STOP instruction.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
153