Printronix L5535, Maintenance Manual

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Chapter 8
Control System Descriptions
corresponds to one pulse) or 1 for phase Z. One encoder revolution is
equivalent to 1/2-inch paper transport. That is, this encoder generates pulses
at a frequency twice as high as that of 400-dpi raster scanning (horizontal
scanning). Also note that a detent current is provided to always stop the motor
with sensing element Z placed in a slotted position.
Since the tractor motor needs to be precision controlled for paper loading or
parking operations, all its pulses are fed back to the MC software, as opposed
to the drum motor and main unit feed motor encoder pulses which are
returned to the driver circuitry.
The MC is interrupted at 281.25 µsec (1/2 of the 400-dpi raster cycle)
intervals under timer control, and control functions (including the transfer
elevator motor ON function) are executed according to the pulse data read
upon encoder interruption. That is, the tractor motor is controlled with double
the 400-dpi accuracy.
MC software