MC68HC908GT16 Datasheet, PDF (352/412 Pages) Motorola, Inc – Microcontrollers

Timebase Module (TBM)
21.4 Functional Description
NOTE: This module is designed for a 32.768-kHz oscillator.
This module can generate a periodic interrupt by dividing the clock
TBMCLK. The counter is initialized to all 0s when TBON bit is cleared.
The counter, shown in Figure 21-1, starts counting when the TBON bit
is set. When the counter overflows at the tap selected by TBR2:TBR0,
the TBIF bit gets set. If the TBIE bit is set, an interrupt request is sent to
the CPU. The TBIF flag is cleared by writing a 1 to the TACK bit. The first
time the TBIF flag is set after enabling the timebase module, the interrupt
is generated at approximately half of the overflow period. Subsequent
events occur at the exact period.
TBMCLK
÷2 ÷2 ÷2
÷2
÷2
÷2
÷2
÷8
÷ 16
÷ 32
÷ 64
÷ 128
TBON
÷2 ÷2 ÷2 ÷2
÷2 ÷2
÷2 ÷2
÷ 2048
÷ 8192
÷ 32768
000
001
010
011
1 0 0 ^SEL
101
110
111
Figure 21-1. Timebase Block Diagram
TBMINT
TBIF
TBIE
R
Technical Data
352
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
Timebase Module (TBM)
MOTOROLA