Deltech Fitness 6 1 0 0, 6 1 0 1 Hardware Safety Features, Watchdog Timer Circuit, CPU/IO, GATE ARRAY, 6Safety Features and Fault Detection, DATA, MOTOR, MOTOR, MEMORY, DRIVER, AUDIBLE

6Safety Features and Fault Detection

Hardware Safety Features

Key hardware safety features include a watch- dog timer circuit, motor driver and motor watchdog circuits, cassette ‘type’ sensor circuit, latch/lock sensor circuit, and a voltage detector circuit. Each safety circuit performs a unique function to insure the overall safety of the device. (See Figure 8.)

Watchdog Timer Circuit

The microprocessor must send an appropriate signal to the watchdog circuit at least once per second. If the microprocessor does not, the watchdog circuit will time out and shut down the pump controller.

Watchdog timer circuitry is provided to monitor the status of the microprocessor and disable the motor and enable the audible alarm if the

microprocessor fails to function properly. The microprocessor must strobe the watchdog circuit at least once every second in order to prevent the watchdog from performing its reset function. The reset output from the watchdog circuit is a pulse output. This acts to “jump start” the microprocessor. This unique feature allows the microprocessor to test the watchdog circuit on every power-up. By setting a flag in memory and not strobing the watchdog, the microprocessor can force a watchdog time-out. After being reset, the microprocessor checks the status flag to see if this was a time-out test. If so, the microprocessor continues normal power-up activities. If the reset occurred when the microprocessor was not expecting it, the microprocessor traps the event, sounds the audible alarm and displays an error message on the LCD.

PROGRAM MEMORY

MB

DATA

MEMORY

MB

		LCD DISPLAY
▼		▼
			▼▼
		CPU/IO/	▼
	▼
		GATE ARRAY	▼▼ ▼
▼
		▼

KEYBOARD

▼		AUDIBLE
		ALARM
▼		VOLTAGE
		REFERENCE
▼		MOTOR
		DRIVER
		▼	▼
	▼
		WATCHDOG
		REAL-TIME
▼		CLOCK

▼

▼

▼

▼

MOTOR

WATCHDOG

VOLTAGE

DETECTOR

SENSORS

Figure 8. CADD-Prizm®pump hardware block diagram.

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