MC68HC908JW32_09 Datasheet, PDF (125/232 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Interrupts
TBR2–TBR0 — Timebase Rate Selection
These read/write bits are used to select the rate of timebase interrupts as shown in Table 9-1.
Table 9-1. Timebase Rate Selection (88-kHz Reference)
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
262144
131072
65536
32768
16384
8192
4096
2048
Timebase Interrupt Rate
Hz
ms
~0.33
~2979
~0.67
~1489
~1.3
~745
~2.7
~372
~5.4
~186
~10.7
~93
~21.5
~47
~43.0
~23
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
TACK — Timebase ACKnowledge
The TACK bit is a write-only bit and always reads as 0. Writing a logic 1 to this bit clears TBIF, the
timebase interrupt flag bit. Writing a logic 0 to this bit has no effect.
1 = Clear timebase interrupt flag
0 = No effect
TBIE — Timebase Interrupt Enabled
This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the
TBIE bit.
1 = Timebase interrupt enabled
0 = Timebase interrupt disabled
TBON — Timebase Enabled
This read/write bit enables the timebase. Timebase may be turned off to reduce power consumption
when its function is not necessary. The counter can be initialized by clearing and then setting this bit.
Reset clears the TBON bit.
1 = Timebase enabled
0 = Timebase disabled and the counter initialized to 0s
9.5 Interrupts
The timebase module can interrupt the CPU on a regular basis with a rate defined by TBR2–TBR0. When
the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase
interrupt, the counter chain overflow will generate a CPU interrupt request. The interrupt vector is defined
in Table 6-3. Interrupt Sources.
Interrupts must be acknowledged by writing a logic 1 to the TACK bit.
MC68HC908JW32 Data Sheet, Rev. 6
Freescale Semiconductor
125