Horizontal Raster Graphics; Horizontal Graphics - Single Density - Texas Instruments 880 User Manual

6.2 HORIZONTAL RASTER GRAPHICS
Horizontal graphics data can be printed at a den-
sity of 60 dots per inch, single density plot mode,
or 120 dots per inch, double-density plot mode.
The vertical density is 144 dots per inch.
6.2.1 Horizontal Raster Data Format/Single-
Density Plot Mode
In single-density plot mode (Figure 6-1), a line of
data containing the control character ENQ (>05,
or hexadecimal 05), indicates that data from the
left margin is horizontal raster data.
Bit 7 of all graphics data bytes must be set (1) for
the data to be treated as graphics data; that is,
valid characters for graphics data are from >40 to
>7F. The low 6 bits are plot data.
The least significant bit (bit 1) is plotted at the left
on the paper, and the remaining plot data bits (2,
3,
4, 5, and 6) are plotted, in order, to the right of
bit 1.
A line feed (>OA) ends a row of data bits and the
next byte of graphics data contains the first six
plot data bits to appear on the next row. When the
printer has stored nine rows, it prints all of them
and moves the paper up nine rows so that the
tenth row of dots will just touch the ninth row.
When a row of raster data is longer than the line
width, extra characters are discarded.
Line termination characters LF and FF cause the
Model 880 Printer to start printing. Two or more
consecutive line feeds, LF (>OA), cause the line
to be printed and the paper to be moved at the
current vertical pitch. A single line feed does not
cause printing unless the last data received was
for the ninth print row. A form feed, FF (>OC),
causes the line to print and the paper to move to
the top of the next form. The carriage return, CR
(>00), causes no printing or paper motion but
allows the row of data to be changed by the next
data line received.
When a data line does not contain the graphics
data character, the remainder of the rows are filled
with "blanks" (>40), and the line is printed. The
printer is now back in the character print mode,
and the paper is moved for the next line of the cur-
rent vertical pitch.
GRAPHICS DATA BYTE
6-4
M~B -~-I-;:-
-5- -4- -3- -2-
Ysl
DATA INPUT (HEX): 4A 4D 7C 05 OA
7E 40 05 OA
4A
~
0 , 10 0
7E
~
0 ,1,
,
PRINTED OUTPUT:
LEFT
MARGIN
,
,
o ,
01
4D
~
0
, ,
01 40
~
0
PLOT DATA
+
o ,
,
o
,1
7C ~
0
+
000
o
01
,1,
,
'st BYTE LSB
2nd BYTE LSB 3rd BYTE LSB
'"
'"
'"
1 2
4 6 1
3 4 6 1 2
4
• * •
* •
* ••
• • * • * •
* •
* • * •
,
Figure 6-1. Horizontal Graphics - Single Density
, 0 01
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