Watchdog Timer; Overview - Renesas H8 Series Hardware Manual

Section 9 Timers
9.6

Watchdog Timer

9.6.1

Overview

The watchdog timer has an 8-bit counter that is incremented by an input clock. If a system
runaway allows the counter value to overflow before being rewritten, the watchdog timer can reset
the chip internally. Note that stabilization times for the H8/38024, H8/38024S, and H8/38024R
Group and for the H8/38124 Group are different.
Features
Features of the watchdog timer are given below.
• Incremented by internal clock source (φ/8192 or φw/32) on the H8/38024, H8/38024S, and
H8/38024R Group.
• On the H8/38124 Group, 10 internal clocks (φ/64, φ/128, φ/256, φ/512, φ/1024, φ/2048,
φ/4096, φ/8192, φw/32, or watchdog on-chip oscillator) are available for selection for use by
the counter.
• A reset signal is generated when the counter overflows. The overflow period can be set from 1
to 256 times the selected clock (from approximately 4 ms to 1,000 ms when φ = 2.00 MHz).
• Use of module standby mode enables this module to be placed in standby mode independently
when not used. See section 5.9, Module Standby Mode, for details.
Rev. 7.00 Mar 10, 2005 page 300 of 652
REJ09B0042-0700