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If you are using a commercial software drawing or graphics pro-
gram such, don't worry about pin numbers with the MPS 1200;
just set the DIP switches accordingly, and select "Commodore" or
"Epson" from the printer options listed in the program.
The MPS 1200 prints dot graphics in lines, just as it does predefmed
characters. The print head moves across the paper striking the
appropriate pins against the ribbon forming a column of dots on
each line. Tall graphics figures are printed by adjusting the line
spacing and printing several lines until the figure is complete.
However, with dot graphics the line length and dot spacing are not
fixed as they are with predefined characters. To use dot graphics,
you must tell the MPS 1200 three things for each line: (1) which
pins to print in each column; (2) how closely to space the columns,
called the graphic density; and (3) how many columns there will be
in the line.
Graphics Commands
The graphics commands perform three functions: they tell the MPS
1200 to interpret the ASCII codes that follow as print head pin
number data instead of characters, they set the graphics density,
and they set the number of columns per line, which tells the MPS
1200 how many pieces of data to expect. First, let's see how the
MPS 1200 prints graphics.
Pin Numbers
To tell the MPS 1200 which pins to print in each column, you need
a way to identify the pins in the print head. The MPS 1200 assigns
each pin a number as shown in Figure 6.1. Skipping the unused
bottom pin, they are numbered as powers of2:
z< ,
21, 22 ... 27, or
in everyday numbers, 1,2,4,8,16,32,64, and 128. Once you've told
the MPS 1200 you are using dot graphics with one of the graphics
commands, you tell it which pins to print by sending the ASCII
code that corresponds to the pin number - one code for each
column.
6-3
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