Section 10 16-Bit Free-Running Timers
10.1 Overview
The H8/534 and H8/536 have an on-chip 16-bit free-running timer (FRT) module with three
independent channels (FRT1, FRT2, and FRT3). All three channels are functionally identical.
Each channel has a 16-bit free-running counter that it uses as a time base. Applications of the
FRT module include rectangular-wave output (up to two independent waveforms per channel),
input pulse width measurement, and measurement of external clock periods.
10.1.1 Features
The features of the free-running timer module are listed below.
Selection of four clock sources
The free-running counters can be driven by an internal clock source (/4, /8, or /32), or an
external clock input (enabling use as an external event counter).
Two independent comparators
Each free-running timer channel can generate two independent waveforms.
Input capture function
The current count can be captured on the rising or falling edge (selectable) of an input signal.
Four types of interrupts
Compare-match A and B, input capture, and overflow interrupts can be requested
independently.
The compare-match and input capture interrupts can be served by the data transfer controller
(DTC), enabling interrupt-driven data transfer with minimal CPU programming.
Counter can be cleared under program control
The free-running counters can be cleared on compare-match A.
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