HP 220 - Manual (Page 59)

5Ć27 Functional Overview C3187Ć90000
FrontĆPanel Interface
The front panel consists of nine LEDs andeight switches. The servo processor interface to
the front panel consists of nine control signals andtwo sense signals.
StepperĆMotor Driver
The servo processor controls a stepper motor usedfor printĆcartridge servicing and
alignment.
CarriageĆProcessor Interface
The servoĆprocessor serial port is usedto communicate with the carriage processor.
Sensors
Four sensors provide input to the servo processor:
D The window sensor is a mechanical switch that detects if the window has been raised.
This serves the purpose of a safety interlock. While the window is raised, the servo
processor halts any carriage movement.
D The media sensor detects the presence of media in the media path. It is also used to
determine media size.
D The pinchĆarm sensor detects whether the pinchĆarms have been raised. The servo
processor uses the sensor to determine the pinchĆarm position during the initialization
sequence.
D The bail sensor detects whether the bail has been raised. The servo processor uses the
sensor to determine the bail position during the initialization sequence.
EEROM
A serial EEROM is usedas nonvolatile storage for calibration andconfiguration data. This
data is typically unique for the plotter. It includes the following information:
D RSĆ232 configurations
D Certain frontĆpanel selections
D PenĆpallet information
D Constants createdduring the various plotter calibrations
The EEROM is solderedto the Main PCA (both new andrebuilt). Shouldthe EEROM be
clearedor the Main PCA replaced, perform all calibrations. (Details ' chapter 7.)
The servo processor drives the EEROM control signals, chip select and shift clock. A reset
signal disables the chip select during power transitions to reduce loss of data.