Printronix p300 Maintenance Manual page 42

2–5. Print State
–continued
e. Plot Mode Operation
Operation in plot mode is similar to character printing except that each line of data produces a single dot
row instead of a full character line.
Normally, plot mode printing occurs only during the left to right shuttle movement. With the double speed
plot jumper W4 installed, however, plot mode printing can be performed in both directions of shuttle
movement.
In plot mode, actual data bits appear on the static RAM output lines, SDB1 through SDB6. An odd dot
decoded plot mode code, hex 05, accompanying the data causes the signal PM to route the buffer output to
the COM line instead of to the character PROMs. A data bit "1" will cause a dot to be printed.
Dots for each six bit code are printed in the odd numbered dot columns within the 0.1 inch character width.
Bit 6 of the code appears at the right side of the printed character column, and bit 1 at the left. A form 13.2
inches wide will accommodate 792 dot columns (6 x 132).
The two plot mode commands, which must accompany each line of plot data, sets the PM flip–flop. When
the dot row is complete, PM is cleared by the term EPFP.
The signal PM inhibits the underline control signal SDUL and enables data bits SDB1 through SDB6 to be
multiplexed to the COM line which is the input to the hammer shift register.
PM also generates the decoded rows per character count signal, EOP, so that each line of data is plotted
without character line definition. Dot rows continuously advance at the standard printing rate, but overall
paper motion depends on the host computer reloading the buffer within stroke time.
The PM signal (instead of the decoded row count) enables the paper feed pulse SPFP to generate EOP .
Even (half) dot plotting may be used to print solid lines, areas of greater density, or to improve resolution.
In even dot plotting, dots are first printed in even numbered dot columns if plot command, hex 04, is sent
with the buffer data. Paper is not advanced for that dot row. The odd column dots are interspersed with dots
printed in even numbered dot columns of that same dot row using hex 05 during loading of the buffer data.
Even dot plotting is specified by the code Hex 04. The decoded command NHDP inhibits the NOPP pulse
from generating a RCLK pulse. This inhibits paper motion. The even dot code and data must precede any
odd dot plot mode code and data. Paper motion occurs only after the odd dot plot shuttle excursion, al-
though a line feed code is used for each data transfer termination in even dot plot.
f. Hammer Driver Circuits (Figure 2–12 and Figure 2–13)
Each of the print hammers (44 for P300/XQ; 66 for P6000/XQ) is controlled by an electromagnetic coil, a
driver, and a logic circuit which, among other functions, controls the energizing of the coil.
2–20 P300/P600 Principles of Operation