Printronix P4280, Maintenance Manual

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E–11 Principles of Operation
Mechanism Driver PCBA
The mechanism driver board, acting on commands from the CCB, controls
real–time operation of the electromechanical printer systems. Functionally,
the board consists of nine subsystems:
•
An 8032 micro–controller that controls ribbon drive and
communication with the CCB.
•
The interface to the power supply board.
•
Pulse–width modulator (PWM) current mode / voltage mode
full–bridge power amplifiers connected directly to the shuttle,
ribbon, paper feed, and platen open motors. Current mode is used
for the paper feed motor, voltage mode is used for the ribbon and
shuttle motors.
•
The paper feed controller (PFC) accepts control codes from the CCB
for each motor phase to vector–control the paper feed motor.
•
The shuttle drive controller receives speed commands from the CCB
through the 8032 micro–controller and commands the speed of the
three–phase dc shuttle motor.
•
The ribbon drive controller, based around the 8032 micro–controller,
receives speed commands from the CCB and drives two dc stepper
motors, regulating the speed and tension of the ribbon and
monitoring the end of ribbon sensors.
•
The platen drive controller for reverse paper feed.
•
Fault detection circuitry samples and senses heat sink temperature,
ribbon speed, shuttle speed, hammer driver circuitry, hammer bank
coil temperatures, power supply voltages, and fault communication
with the CCB.
•
Circuitry that registers magnetic pick–up unit (MPU) output,
processes it for the logic interface, and sends it to the CCB for
timing hammer fire.
The Ribbon Drive System
The ribbon drive system is controlled by the 8032 micro–controller. The
CCB sends commands to the 8032 to start and stop the ribbon, set the ribbon
speed, and apply slack or tension to the ribbon. The real–time control
functions are done by the 8032, acting in accordance with firmware control
algorithms and look–up tables. The 8032 communicates with an ASIC to