Salter Brecknell 1200 Series - Manual (Page 32)

Model 122X MiniPrinter User’s Manual 32
The mechanism used in the printer prints one line of
dots across at a time. This means that when it prints
one line of characters it has actually printed ten lines
of dots where the first eight lines make up the
character and the last two lines are blank for the
space between character lines. By using the
CHR$(18) control code, you can tell the printer which
dots to print for one whole dot line. Since there are
144 dots per line, you must follow the CHR$(18)
control code with 144 bits of information. For every
place there is a one in the 144 bit pattern you send,
the printer will print a dot. Rather than receive one bit
at a time the printer expects to receive the information
eight bits at a time. This means that after receiving a
CHR$(18) the next eighteen 8 bit characters it
receives will be printed as dots to form one dot line.
To figure out the dot pattern values to send after the
CHR$(18), you will need some grid paper. A large
sheet with 144 grid boxes across would be conve-
nient. If such a large sheet of paper is not available,
you could divide your pattern in half and work with 72
grid boxes across. Divide up your grid paper by
drawing a heavy line down every 8 boxes across.
Now fill in each box of the grid that you want to be
printed. Now do the following procedure to compute
the eighteen values which describe your desired bit
pattern.
Imagine placing the number sequence over each of
the first eight grid boxes.
Now add together all the numbers above the boxes
which are filled in or have a dot as in the example
above. In our example, we would have 2 + 16 + 32
which equals 50. ‘50’ then would be the first entry of a
data statement which would be followed by seventeen
more numbers computed in the exact same manner
as the example. Once you have the eighteen values
in a data statement, you need simply run a program
which prints a CHR$(18) followed by the data value
read from the data statement. Don’t forget to end all
of your print statements with semicolon. This will
prevent carriage returns CHR$(13) from being sent,
which would become part of the eighteen data values
for which the printer is waiting.
Dot Graphics
Code 18