Commodore MPS 1200 - Putting It All Together

Why two numbers? Consider the maximum number of columns
that can be printed in a line. At 60 dots per inch, the MPS 1200 can
print 480 columns of dots in an 8-inch line. And at 240 dots per inch
the
MPS 1200 can print 1,920 columns in a line! But the largest
number BASIC can send is 255. Obviously, you need a way to
send larger numbers.
The MPS 1200 solves this problem by using the two numbers nl
and n2 together to determine the number of columns in a line. The
first number, nl, indicates the number of columns from 0 to 255.
The second number, n2, indicates the number of times 256 is to be
added to the first
number. With this scheme you can send any size
number you need.
You can calculate the values of n1 and n2 for any number of
columns you need by dividing the number of columns by 256. The
quotient will be n2 and the remainder will be n1. If you like, you
can calculate n1 and n2 with two expressions:
N2 = INT (X/256)
N1 = X-(256*N2)
where x'is the number of columns. Table 6-1 shows another easy
way to calculate n1 and n2.
Table 6-1. Calculating n1 and n2.
If the number of columns (x) ranges from:
n1 is:
1 to 255
256
to 511
512 to 767
768 to 1023
1024 to 1279
1280 to 1535
1536 to
1791
1792 to 1920
x
x-256
x-512
x-768
x-1024
x-1280
x-1536
x-1792
Putting It All Together
and n2 is:
o
1
2
3
4
5
6
7
Now that we know how the graphics commands work, how to
control the pins, and how to set the number of columns, let's try .1
sample program to see some actual graphics.
6-7