MC68HC908GP32 Datasheet, PDF (338/410 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Freescale Semiconductor, Inc.
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 crystal
frequency, CGMXCLK. 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.
CGMXCLK
÷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
336
MC68HC908GP32•MC68HC08GP32 — Rev. 6
Timebase Module (TBM)
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