MC68HC908AP16CFB datasheet(206/440 Pages) MOTOROLA

206 / 440 page

Timebase Module (TBM)

Data Sheet

MC68HC908AP Family — Rev. 2.5

206

MOTOROLA

12.3 Functional Description

This module can generate a periodic interrupt by dividing the oscillator

clock frequency, OSCCLK. The counter is initialized to all 0s when

TBON bit is cleared. The counter, shown in Figure 12-1, starts counting

when the TBON bit is set. When the counter overflows at the tap

selected by TBR[2:0], 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.

The reference clock OSCCLK is derived from the oscillator module, see

7.2.2 TBM Reference Clock Selection.

Figure 12-1. Timebase Block Diagram

(See Section 7. Oscillator (OSC).)

÷ 2

SEL

0 0 0

0 0 1

0 1 0

0 1 1

TBIF

TBIE

TBON

1 0 0

1 0 1

1 1 0

1 1 1

OSCCLK

÷ 2

÷ 8

÷ 16

÷ 32

÷ 64

÷ 2048

÷ 32768

÷ 65536

÷ 131072

TBMINT

÷ 2

÷ 262144

From OSC module

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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