MC908AZ32ACFUE Datasheet, PDF (207/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 19
Timer Interface Module B (TIMB)
19.1 Introduction
This section describes the timer interface module (TIMB). The TIMB is a 2-channel timer that provides a
timing reference with input capture, output compare and pulse width modulation functions. Figure 19-1 is
a block diagram of the TIMB.
19.2 Features
Features of the TIMB include:
• 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 Pulse Width Modulation (PWM) Signal Generation
• Programmable TIMB Clock Input
– 7 Frequency Internal Bus Clock Prescaler Selection
– External TIMB Clock Input (4 MHz Maximum Frequency)
• Free-Running or Modulo Up-Count Operation
• Toggle Any Channel Pin on Overflow
• TIMB Counter Stop and Reset Bits
19.3 Functional Description
Figure 19-1 shows the TIMB structure. The central component of the TIMB is the 16-bit TIMB counter that
can operate as a free-running counter or a modulo up-counter. The TIMB counter provides the timing
reference for the input capture and output compare functions. The TIMB counter modulo registers,
TBMODH–TBMODL, control the modulo value of the TIMB counter. Software can read the TIMB counter
value at any time without affecting the counting sequence.
The two TIMB channels are programmable independently as input capture or output compare channels.
19.3.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs or the TIMB clock pin, PTD4/ATD12.
The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIMB status and control register select the TIMB clock source.
MC68HC908AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
207