3 Software

The software is used to communicate with the user, through the keyboard and the display, and to control the plotter according to the users wish. The software is written entirely in assembler for 68008

Software flowchart.

3.1 Linedrawing Algorithm

Computes the movement required to move on a straight line from the actual position to the user input coordinates.

Linedrawing flowchart (in swedish - sorry).

Initially, the moving distance in x-axis is compared to the one along the y-axis to find the one with largest unsigned value. All further calculation is based on that value. The distances are examined in sense of sign, which will give the direction of the pulse sequence sent to the step-motor. The qoute between the movement distances is calculated as an integer and stored away. The modulus, created by the integer division:

$$\frac{\Delta M}{\Delta m}=qouta,modulus$$

$\Delta$M

the major moving distance

$\Delta$m

the minor moving distance

is multiplied with 20, and divided by to get the compensation to be added to achieve the wanted precision. The actual movement is divided into intervals, which consists of the qouta+the compensation in the first axis and one step in the second axis. This interval is cycled until the wanted coordinate is achieved.