Fault Monitoring - Printronix P4280 Maintenance Manual

Mechanism Driver Interface The paper feed controller (PFC) directs all
paper motion. During printing, it usually moves paper in response to a trigger
from the FTIC, which synchronizes paper motion with shuttle motion. The
64180 programs the PFC 8032 at the beginning of each dot row, telling the
PFC how far to move when the trigger is received. The PFC sets up for the
move, waits, then moves when the trigger occurs. The other method of
starting paper motion is with a command passed through the inter–processor
port (an eight bit parallel port between the 8032 and the 64180). This results
in immediate movement. Other paper commands and status signals are also
passed through this port.
Ribbon and Shuttle Motion The 64180 interfaces through its second
UART to the ribbon / shuttle processor (RSP) on the mechanism driver
board. The 64180 begins all transactions on the serial interface; the RSP sets
a bit in the 64180 hardware status register when it needs service.

Fault Monitoring

The RTPU 64180, the PFC 8032, and the RSP monitor different functions for
faults. The 64180 looks for hammer driver faults, shuttle stalls, and an open
platen. The PFC 8032 monitors paper out and the paper motion detector. The
RSP watches for faults in the motor drive circuits. The PFC and RSP report
errors to the 64180, which collates fault status and passes it on to the DPU
68010 processor.
Hammer Bank and Hammer Driver Faults The 64180 and FTIC check
the hammer driver and hammer bank for faults on every shuttle stroke. Faults
are detected by circuits on the mechanism driver board and relayed to the
CCB. Fault circuitry can detect shorted coils and rising temperatures in the
coils. One coil is checked on every shuttle stroke; 48 shuttle strokes are
required to check all coils. When the RTPU is notified of a fault, it sends a
message to the 68010. If a coil shorts, the 64180 stops printing before firing
another dot row.
Paper Faults The PFC 8032 monitors paper faults and reports them to the
64180 through the eight bit parallel port they share. The PFC works with a
friction wheel paper motion detector and a reflective (optical) paper out
sensor. The sensors interface directly to the CCB; there are analog circuits on
the CCB to condition the sensor inputs.
Ribbon and Shuttle Faults The RSP monitors ribbon and shuttle faults
and reports them to the 64180 over the serial interface.
Principles of Operation E–9