mc68hc08ln56 Freescale Semiconductor, Inc, mc68hc08ln56 Datasheet - Page 219

• Manufacturer Part Number: mc68hc08ln56
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 20
Time Base Module (TBM)
20.1 Introduction
The time base module consists of a counter clocked by the crystal clock, which will generate periodic
interrupts at user selectable rates.
20.2 Features
Software programmable 1-Hz, 4-Hz, 16-Hz, and 256-Hz periodic interrupt using 32.768-kHz crystal.
20.3 Functional Description
This module can generate a periodic interrupt by dividing the crystal frequency, CGMXCLK. The counter
is initialized to all zeros when TBON bit is cleared. The counter, shown in
when the TBON bit is set. When the counter overflows at the tap selected by TBR1: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 one to the TACK bit. The first time the TBIF flag is set after enabling the time base module, the interrupt
is generated at approximately half of the overflow period. Subsequent events occur at the exact period.
Freescale Semiconductor
XTAL
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This module is designed for a 32.768-kHz oscillator.
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MC68HC08LN56 • MC68HC708LN56 General Release Specification, Rev. 2.1
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Figure 20-1. Time Base Block Diagram
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NOTE
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TBON
Figure
R
20-1, starts counting
TBIF
TBMINT
TBIE
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