Usage Note - Renesas H8/3847R Series Hardware Manual

8-bit single-chip microcomputer super low power

Table of Contents

Section 9 Timers

Usage Note

Note the following regarding the operation of timer C.

(1) Counting errors caused by external event input

Timer counter errors may occur under the following conditions.

An external event (TMIC) is used in subsleep mode.

The counter increments or decrements twice for a single external event input.

Approximate rate of occurrence

The approximate rate of occurrence in cases where the external event input is not

synchronized with internal operation is defined by the following equation.

Approximate rate of occurrence P = 30 ns / tsubcyc

For example, if tsubcyc = 61.06 µs (subclock φw/2), P = 0.0005 (0.05%). If 2,000 external

event inputs occur, there is a likelihood that one of them will cause the counter to

increment or decrement twice (+2 or –2).

The symptom described is caused by the internal circuit configuration of the device and

therefore difficult to avoid. Therefore, it is not advisable to use the clock counter for

applications requiring a high degree of accuracy.

Rev. 6.00 Aug 04, 2006 page 274 of 680

REJ09B0145-0600