Functional Description - Motorola MC68HC908GP32 Technical Data Manual

Timebase Module (TBM)

21.4 Functional Description

NOTE:
÷ 2 ÷ 2
CGMXCLK
÷ 2 ÷ 2
Technical Data
336
Freescale Semiconductor, Inc.
This module is designed for a 32.768-kHz oscillator.
This module can generate a periodic interrupt by dividing the crystal
frequency, CGMXCLK. The counter is initialized to all 0s when TBON bit
is cleared. The counter, shown in
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.
÷ 2 ÷ 2 ÷ 2
÷ 8 ÷ 16 ÷ 32
÷ 2 ÷ 2 ÷ 2 ÷ 2
÷ 2048 ÷ 8192
Figure 21-1. Timebase Block Diagram
Timebase Module (TBM)
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Figure
÷ 2 ÷ 2
÷ 64 ÷ 128
÷ 2 ÷ 2
÷ 32768
0 0 0
0 0 1
0 1 0
0 1 1
SEL
1 0 0
1 0 1
1 1 0
1 1 1
MC68HC908GP32
21-1, starts counting when the
TBON
TBMINT
TBIF
R
MC68HC08GP32
•
MOTOROLA
TBIE
Rev. 6
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