Specifications

2–24
Principles of Operation
Start / Stop Ribbon
The ribbon motors are started and stopped by a digital signal from the
controller board. After a stop signal is received, the ribbon is locked to
maintain tension. If the controller board sends a slack signal, the PWM
amplifiers are tri–stated.
The Shuttle Drive System
The shuttle drive system is an analog closed–loop speed controller that
accepts commands from the controller board through the 8032
microcontroller and MDIC ASIC. The controller board writes a word
containing start, stop, and speed data to the 8032, which in turn writes a word
to the MDIC. The MDIC generates a clock signal based on this word.
The shuttle is protected from overspeed and over current.
The Paper Feed System
Dot row advance and slew tables are stored in the controller board The paper
feed drive circuit takes commands directly from the controller board to
control the two–phase DC paper feed stepper motor. A controller board paper
feed command is a digital word containing a value proportional to the desired
current level in the paper feed motor, enabling the motor to be
quarter–stepped. Two PWM current mode amplifiers, protected against
overloads and short circuits, drive the paper feed motor. The paper feed
motor is usually energized whenever printer power is on in order to maintain
tension and position of the paper. The paper feed motor is disabled in a
platen open, paper jam, or paper out fault condition.
The Reverse Paper Feed System
To reverse paper motion, the printer must open the platen, move the paper
backwards vertically, close the platen, and remove the slack in the paper. A
platen open or close command is generated on the controller board and
communicated to the RSP 8032 processor. The RSP generates control and
step clock signals for the platen driver circuitry. The platen driver circuitry is
connected to a stepper motor that drives the platen through a toothed belt.
The platen motor is only energized during the open and close cycles. The
platen driver is protected from over current.