Printronix L5000 Series Maintenance Manual page 283

Data output from the digital control unit is equivalent to 1V per 1 bit, and at the D/A
converter, –8–+8V are output according to inputs of 0000–1111. (Note that 0000 is
0V). This is the voltage calculated from pulse string comparison, but different
outputs are required for positive rotation, negative rotation, and detent (keeping
position). Therefore there are 3 variable resistors connected to the D/A converter, so
that voltage can be adjusted to obtain output for positive, negative, and inverse. And,
depending on whether the motor is in the condition of positive, negative, or inverse,
the analog switch connected to these variable resisters is switched accordingly by
PFEED (positive rotation), PBACK (negative rotation), or PDNT (detent rotation)
signals, and control voltage is obtained.
In case of either positive rotation, negative rotation, or inverse, the driver circuit is
controlled by linear system by the operational amplifier which has +24V and –24V as
the power supply, and controls rotation speed by negative feedback of current that
has flowed through the motor, to the input side.
Further, for stopping the motor, voltage is selected to adjust motor torque and keep
the position where Z phase of the encoder is detecting slit. If the encoder is off of this
and A phase and B phase pulses are detected, current that will cause as many back
rotations as pulses detected is sent to the motor.
Electrical and Wire Data 6–45