The 80C320 provides two new features to handle power failure conditions. The first feature is an automatic power failure reset and the other is a power failure interrupt.
Power Failure Reset
The 80C320 is equipped with an automatic power failure reset. This means that if the operating voltage drops below Vrst (see
chip spec sheet), the microcontroller will automatically enter a reset mode. The chip will remain in reset mode until normal operating voltage is restored. This reset is performed automatically requiring no special action on the part of the software or of the user.
Interesting Fact: This feature is important. A normal 8051, without such a feature, continues to run "normally" as power dips below the minimum. However, the 8051 may begin to execute bogus instructions and/or starts writing/reading incorrect values to and from memory locations. The power failure reset feature on the 80320 prevents a low power condition from causing strange and unexpected program behavior.
Power Failure
Interrupt
A new interrupt can
be enabled which is
triggered when the
operating voltage drops
below Vpfi (see
chip spec sheet.)
This can be useful to
make preparations for a
power failure.
WDCON.5 (EPFI)
is the enable for the
Power Failure Interrupt.
When this bit is set, a
low operating voltage
will trigger the
interrupt. When the bit
is clear, the interrupt
will not be triggered.
WDCON.4 (PFI)
is the flag that is set
when the power falls
below Vpfi. If the
interrupt is enabled
(via bit EPFI), an
interrupt will be
triggered when this bit
is set. Even if the
power failure interrupt
is not set, this bit
will be set to reflect a
low-power status.
Once PFI is
set by the hardware,
software must clear it
manually. The bit will
not be cleared
automatically.
The interrupt vector
for the power failure
interrupt is 0033h. Click
here for
>>>>
Dallas
80C320 -
Chapter
4.1 (Power
Failure
Reset) |
