Deltec Cozmo Uživatelský manuál stáhnout pdf (Strana 129)

Technical Information

117

verifies this function during the watchdog test described

above.

Voltage detector circuit

Low voltage detection is performed by part of the

watchdog circuit and by the microprocessor via soft-

ware. 3 low voltage levels are detected. The first 2 levels

are detected by software and the 3rd by hardware. The

1st 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

available. An Analog to Digital Converter (ADC) built

into the microprocessor allows the microprocessor, via

software, 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 software 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 opera-

tion of the microprocessor cannot be guaranteed, a

hardware reset circuit is triggered which places the

microprocessor in reset. This prevents ambiguous

microprocessor operation as the battery voltage contin-

ues to decay. The 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 thereafter, 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

software stops insulin 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 differ-

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