Technical Information
77
Voltage detector circuit
Low voltage detection is performed by part of the watch-
dog circuit and by the microprocessor via soware.
ree low voltage levels are detected. e rst two levels
are detected by soware and the third by hardware.
e rst level to be reached is the Low Battery Warning
threshold, which occurs when the battery voltage decays
to a point where less than 10% operating time is avail-
able. An analog to digital converter (ADC) built into the
microprocessor allows the microprocessor, via so-
ware, to monitor the battery voltage. At the Low Battery
Warning threshold, the microprocessor enables an alarm
(either beep or vibrate) and displays the low battery alert
in the display. When the battery voltage drops to a point
where it is too low to guarantee proper motor operation,
the microprocessor via soware stops delivery, generates
an alarm (either beep or vibrate), and a depleted battery
alarm message appears in the display. When the battery
voltage drops to a value where operation of the micro-
processor cannot be guaranteed, a hardware reset circuit
is triggered which places the microprocessor in reset.
is prevents ambiguous microprocessor operation as
the battery voltage continues to decay. e hardware
reset continues until the battery is completely depleted
or it is removed. Once the pump controller goes into low
battery shutdown, only replacing the depleted battery
with a new battery will clear the condition.
Software safety features
Hardware-related software safety features
Program memory check
At power up and regular intervals thereaer, the pro-
gram memory is tested by calculating a cyclic redun-
dancy code (CRC) on the program and then comparing
it with the CRC stored with the program.
If the stored and calculated CRC do not match, the
soware stops medication delivery, initiates an alarm
(either beep or vibrate) and a system fault alarm message
appears in the display.
RAM memory check
At power up, the random access memory (RAM) is
checked. A series of bit patterns is written to and read
from each address in the RAM. If the read data is dier-
ent from the written data, the soware stops medication
delivery, initiates an alarm (either beep or vibrate) and a
system fault alarm message appears in the display.
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