Digital Equipment RW504-ZA, Service Manual

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ROM. The controller firmware resides in two FLASH ROMs. These FLASH
ROMs allow new firmware versions to be downloaded into ROM in the field.
RAM. The two RAM chips are special, low-power CMOS static RAMs. A standby
battery on the PCA takes over powering these chips if main power is lost. The
chips remain in standby mode, providing a nonvolatile memory storage capability
when the unit is powered off.
The PULSE WIDTH MODULATION (PWM) amplifier takes the signals from
the MCC changes them into voltages form the picker motor and carriage motor.
Motor speed control is by feedback from the picker and carriage motors through Z
and Y encoders back to the MCC.
The vacuum filament display uses a 7.5-volt supply tied to a 5-volt reference
resulting in an exitation voltage of from two to three volts. The grids of the
display are at approximately 20 volts.
The SCSI INTERFACE is the SPIFI chip. All SCSI protocol is handled by the
SPIFI under control of the main 68000 processor.
The MULTIFUNCTION PERIPHERAL chip controls interrupts, RS-232
functions, and certain timers throughout the controller PCA.
The SERVO, I/O, and SENSORS circuitry handle the servo communications (e.g.
shutdown control), I/O communications (e.g. drive eject and drive busy), and
sensor communications (e.g. mailslot sensor and vertical calibration sensor).
6–6 Theory of Operation