Print State - Printronix p300 Maintenance Manual

2–5. Print State
a. General (Figure 2–5)
During this state, a complete line of data is printed, and while this is occurring, the paper advances, one dot
row at a time, within the character line.
The print state is entered at the end of the buffer load state when each one of the following conditions ex-
ists:
–Printable characters are in the buffer; NPTCH is true.
–The end of data transfer is reached; EDT is true (any paper motion command can signal the end of
data transfer).
–The shuttle is up to speed; SUS is true.
–RESYNC occurs.
When no plot mode command is present, the print buffer bytes address character patterns in the character
generator PROMs. As the shuttle scans back and forth, dot rows are printed in accordance with those pat-
terns. When a plot mode command is received, the print buffer byte bypasses the character generator
PROMs and goes directly to the COM line via a multiplexer.
The print state ends when the last dot row of a line has been printed, that is, EOP becomes true.
The following printer functional elements are discussed in this paragraph:
ELEMENT
Character Generation
Character Generation Logic
Dot Row Counter Logic
Plot Mode Operation
Hammer Driver Circuits
Safety Circuits
Hammer Reset Timer
Print Synchronization
Print Mechanism
b. Character Generation (Figure 2–6 through Figure 2–8)
The complete character line (132, 176, or 220 eight bit bytes for P300; 132 or 198 for P600) stored in the
buffer is addressed sequentially by the static RAM counter as it is clocked by SRCLK. Each byte ad-
dressed is read out as data bits SDB1 through SDB8 and applied to the PROM address control logic deter-
mining PROM selection and to the character PROMs themselves.
Dot patterns for each character set are stored in individual character PROM addresses. Each dot pattern is
formed in a matrix 12 dot columns wide and 9 dot rows high. Nine of the 12 dot columns are used for the
character and three for the space between characters.
An uppercase character matrix occupies the top seven horizontal dot rows, while the two bottom rows and
three additional rows remain blank for the space between lines.
2–10
SUBPARAGRAPH
b
c
d
e
f
g
h
i
j
P300/P600 Principles of Operation