mc68hc912bc32 Freescale Semiconductor, Inc, mc68hc912bc32 Datasheet - Page 159

• Manufacturer Part Number: mc68hc912bc32
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 13
Enhanced Capture Timer (ECT) Module
13.1 Introduction
The M68HC12 enhanced capture timer (ECT) module has the features of the M68HC12 standard timer
(TIM) module enhanced by additional features in order to enlarge the field of applications.
These additional features are:
This section describes the standard timer found on the MC68HC912B32 as well as the additional features
found on the MC68HC12BE32.
13.2 Basic Timer Overview
The basic timer consists of a 16-bit, software-programmable counter driven by a prescaler. This timer can
be used for many purposes, including input waveform measurements while simultaneously generating an
output waveform. Pulse widths can vary from microseconds to many seconds.
A full access for the counter registers or the input capture/output compare registers should take place in
one clock cycle. Accessing high byte and low byte separately for all of these registers may not yield the
same result as accessing them in one word.
13.3 Enhanced Capture Timer Modes of Operation
The enhanced capture timer has eight input capture, output compare (IC/OC) channels same as on the
M68HC12 standard timer (timer channels TC0–TC7). When channels are selected as input capture by
selecting the IOSx bit in the timer input capture/output compare select register (TIOS), they are called
input capture (IC) channels.
Four IC channels are the same as on the standard timer with one capture register which memorizes the
timer value captured by an action on the associated input pin. Four other IC channels, in addition to the
capture register, also have one buffer called holding register. This permits the register to memorize two
different timer values without generation of any interrupt.
Four 8-bit pulse accumulators are associated with the four buffered IC channels. Each pulse accumulator
has a holding register to memorize their value by an action on its external input. Each pair of pulse
accumulators can be used as a 16-bit pulse accumulator.
Freescale Semiconductor
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16-bit buffer register for four input capture (IC) channels
Four 8-bit pulse accumulators:
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16-bit modulus down-counter with 4-bit prescaler
Four user selectable delay counters for input noise immunity increase
Main timer prescaler extended to 7-bit
8-bit buffer registers associated with the four buffered IC channels
Configurable as two 16-bit pulse accumulators
M68HC12B Family Data Sheet, Rev. 9.1
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