Eurotech ZEUS, Technical Manual

Page: 32 / 136

ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D
32
Watchdog timer
The ZEUS uses an external watchdog timer (MAX6369) which can be used to protect
against erroneous software. This is a programmable watchdog timer that can be
adjusted for timeout periods of 1ms, 10ms, 30ms, 100ms, 1s, 10s and 60s. The board
is reset when timeout occurs. The MAX6369 watchdog timer can be programmed
using the WD setup register provided within the CPLD. The register is memory
mapped (accessible through CS5#). The WDT is disabled upon reset, and remains so
until enabled by the software.
The following table shows the WD setup register bit definitions:
Watchdog Register [REG3]
Bits Description
7:4 Not used.
3 WDI: Watchdog Input. If WDI remains either high or low for the
duration of the watchdog timeout period (t
WD
), WDT triggers a reset
pulse. The internal watchdog timer clears whenever a reset pulse
is asserted or whenever WDI sees a rising or falling edge.
2:0 WDSET[2:0] – watchdog enable / timeout period setup bits.
Hex Offset Address:
0x13800000
Reset Hex Value:
0x03
Access:
Read/write
For further details, see the
Intel PXA27x Processor Family Developer’s Manual
on the
Development Kit CD.