Printronix P9212 - Fault Monitoring

2–30
Principles of Operation
with a command passed through the inter–processor parallel port. This
results in paper movement that begins immediately. Other paper commands
and status signals are also passed between processors through this port.
Ribbon and Shuttle Motion The Z8S180 interfaces through its internal
UART to the ribbon / shuttle processor (RSP) on the mechanism driver
board. The Z8S180 begins all transactions on the serial interface, so there is a
bit in the Z8S180 hardware status register that the RSP sets to tell the
Z8S180 when it needs service. The Z8S180 polls this bit regularly; if it is
true, the Z8S180 initiates service over the serial interface by asking the RSP
what it needs.
Fault Monitoring
The RTPU Z8S180, the PFC 8032, and the RSP monitor different functions
for faults. The Z8S180 looks for hammer driver faults, shuttle stalls, and an
open platen. The PFC 8032 monitors the paper motion detectors. The RSP on
the mechanism driver board watches for faults in the motor drive circuits.
The PFC and RSP report errors to the Z8S180, which collates fault status and
passes it on to the DPU.
Hammer Faults The Z8S180 and FTIC check the hammer driver and
hammer bank for faults on every shuttle stroke. Faults are detected by
circuits on the mechanism driver and hammer driver boards and relayed to
the LMI. Fault circuitry can detect rising temperatures in the coils. One coil
is checked on every shuttle stroke; therefore, 88 shuttle strokes are required
to check all coils. When the RTPU is notified of a fault, it sends a message to
the 68EC030. The hammer driver and mechanism driver boards also
continuously monitor for shorts in hammer driver circuits and cables. If they
detect currents that can harm the hammer bank, the +48 volt power supply is
shut down within 70 milliseconds by “crowbar” circuitry.
Paper Faults The PFC 8032 monitors paper faults and reports them to the
Z8S180 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 LMI; analog circuits on the LMI
board condition the sensor inputs.
Ribbon and Shuttle Faults The RSP monitors ribbon and shuttle faults and
reports them to the Z8S180 over the serial interface.