MVME5100 Single Board Computer Programmer's Reference Guide

Registers
KEY Key. This field is used during the two step arming process
of the Control register. This field is sensitive to the
following data patterns:
PATTERN_1 = $55
PATTERN_2 = $AA
The Control register will be in the armed state if
PATTERN_1 is written to the KEY field. The Control
register will be changed if in the armed state and
PATTERN_2 is written to the KEY field. An incorrect
sequence of patterns will cause the Control register to be
in the unarmed state.
A value of all zeros will always be returned within the
KEY field during read cycles.
ENAB ENAB. This field determines whether or not the WDT is
enabled. If a one is written to this bit, the timer will be
enabled. A zero written to this bit will disable the timer.
The ENAB bit may only be modified on the second step
of a successful two step arming process.
ARM ARMED. This read-only bit indicates the armed state of
the register. If this bit is a zero, the register is unarmed. If
this bit is a one, the register is armed for a write.
RES RESOLUTION. This field determines the resolution of
the timer. The RES field may only be modified on the
second step of a successful two step arming process. The
following table shows the different options associated
with this bit.
RES Timer Resolution Approximate Max
Time
0000 1 us 64 msec
0001 2 us 128 msec
0010 4 us 256 msec
0011 8 us 512 msec
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