MC68HC908QC16_07 Datasheet, PDF (205/274 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 17
Timer Interface Module (TIM2)
17.1 Introduction
This section describes the timer interface module (TIM2). The TIM2 module is a 2-channel timer that
provides a timing reference with input capture, output compare, and pulse-width-modulation functions.
The TIM2 module shares its pins with general-purpose input/output (I/O) port pins. See Figure 17-1 for
port location of these shared pins.
17.2 Features
Features include the following:
• Two input capture/output compare channels
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
• Buffered and unbuffered output compare pulse-width modulation (PWM) signal generation
• Programmable clock input
– 7-frequency internal bus clock prescaler selection
– External clock input pin if available, See Figure 17-1
• Free-running or modulo up-count operation
• Toggle any channel pin on overflow
• Counter stop and reset bits
17.3 Functional Description
Figure 17-2 shows the structure of the TIM2. The central component of the TIM2 is the 16-bit counter that
can operate as a free-running counter or a modulo up-counter. The counter provides the timing reference
for the input capture and output compare functions. The counter modulo registers, T2MODH:T2MODL,
control the modulo value of the counter. Software can read the counter value, T2CNTH:T2CNTL, at any
time without affecting the counting sequence.
The two TIM2 channels are programmable independently as input capture or output compare channels.
17.3.1 TIM2 Counter Prescaler
The TIM2 clock source is one of the seven prescaler outputs or the external clock input pin, T2CLK if
available. The prescaler generates seven clock rates from the internal bus clock. The prescaler select
bits, PS[2:0], in the TIM2 status and control register (T2SC) select the clock source.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 3
Freescale Semiconductor
205