SPMCK16Z4MPV20 datasheet(265/500 Pages) FREESCALE

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M68HC16 Z SERIES

GENERAL-PURPOSE TIMER

USER’S MANUAL

11-1

SECTION 11

GENERAL-PURPOSE TIMER

This section is an overview of the general-purpose timer (GPT) function. Refer to the

GPT Reference Manual (GPTRM/AD) for complete information about the GPT mod-

ule.

11.1 General

The 11-channel general-purpose timer (GPT) is used in systems where a moderate

level of CPU control is required. The GPT consists of a capture/compare unit, a pulse

accumulator, and two pulse-width modulators. A bus interface unit connects the GPT

to the intermodule bus (IMB). Figure 11-1 is a block diagram of the GPT.

The capture/compare unit features three input capture channels, four output compare

channels, and one channel that can be selected as input capture or output compare.

These channels share a 16-bit free-running counter (TCNT) that derives its clock from

a nine-stage prescaler or from the external clock input signal, PCLK.

Pulse accumulator channel logic includes an 8-bit counter. The pulse accumulator can

operate in either event counting mode or gated time accumulation mode.

Pulse-width modulator outputs are periodic waveforms whose duty cycles can be in-

dependently selected and modified by user software. The PWM circuits share a 16-bit

free-running counter that can be clocked by the same nine-stage prescaler used by

the capture/compare unit or by the PCLK input.

All GPT pins can also be used for general-purpose input/output. The input capture and

output compare pins form a bidirectional 8-bit parallel port (port GP). PWM pins are

outputs only. PAI and PCLK pins are inputs only.

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