Abbott VP 2000 Service Manual page 60

Technical Data
3-24
Polled stimuli:
• Flow, Recirculate, Soak buttons
• Position sensors
• Motor speed and direction calculation
• Hood-Interlock sensors
• Response to computer interface commands
Interrupting stimuli and actions:
• Internal clock
• IBM type computer interface
• Stepper motor control
• Control of the display and keyboard
The program checks the polled stimuli in a control loop. If one
of the stimuli is active, it is handled. Then the program goes to
the state software to see if any stimuli specific to the present
state are active. This flow goes on continually. All the while, an
internal timer interrupts the program 2400 times per second.
When interrupted, program stops what it is doing, and goes to
a special section called the interrupt handler. There, the
position sensors are read, timers are kept current, the
computer interface is checked for characters coming in, and
the stepper motors are stepped if necessary. At the end,
operation is resumed exactly where it was interrupted.
Section 3
Abbott VP 2000™ Processor Service Manual
30-608308//R1—September 2008