I think you need to program your own ellipse and provide the dotted
pseudo code:
for (float angle = 0; angle < 360; angle += 20) {
x=cos(radians(angle)) .... ;
y=cos(radians(angle)) .... ;
point(x,y);
}
Full Code
size(1200, 700);
background(0);
stroke(255);
for (int angle = 0; angle < 360; angle += 3) {
float x=cos(radians(angle))*200 + 300 ;
float y=sin(radians(angle))*200 + 300 ;
point(x, y);
}