Paper Feed State - Printronix p300 Maintenance Manual

2–6. Paper Feed State
a. General
During the paper feed state, paper is advanced to the top of the next character line after printing has been
completed, or it is slewed several lines under the direction of either the EVFU or a top of form command.
The paper feed state can be entered from either the buffer load or print state when the paper feed flip–flop,
PPF, is set. When the printer is in the buffer load state, and a paper motion command is received without a
printable character, the paper feed state is entered directly.
When the printer is in the print state, PPF is set by EOP at the next CLKB count. EOP becomes true when
the dot row counter has counted the seventh row of an uppercase character or the ninth row of either under-
lines or a lowercase character with descenders and that row has been printed.
Paper feed is implemented by the paper tractors driven by a four phase stepper motor. The speed of this
motor is governed by a velocity PROM addressed by a high speed counter to supply a specific paper move-
ment acceleration/deceleration profile that concerns dot row count. In addition, the paper feed velocity
counter sends paper feed signals, PF1/PF2, to the paper feed control where they are developed into drive
currents to turn the paper feed motor.
The number of paper feed pulses sent to the drive circuits and the dot row count that resets the row counter
both depend on which one of the following types of paper advancement are being activated:
–Advance to the next dot row within a character line during print state operation.
–Advance from the last printed row of a character line to the top row of the next character line.
–Advance or slew through one or more character lines without printing because of a line feed or skip–
over perforation command.
–Slew to the top of form.
–Advance or slew under EVFU control.
The following functional elements are discussed in this paragraph:
Paper Feed to Next Dot Row
Paper Feed to Next Character Line
Skip Over Perforation
Paper Feed to Top of Form
Electronic Vertical Format Unit
Programming EVFU Memory
Channel Seek Operation
Vertical Tab Operation
Binary Count Operation
Runaway Paper Fault Protection
Paper Transport
Paper Out Switch Logic
P300/P600 Principles of Operation
ELEMENT SUBPARAGRAPH
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