HW 10-1 Creating PWM Spice block.

Hi,

I've read in the text that the PWM block is modeled in Spice as simply vx/VM where vx is the input and VM is the sawtooth peak value. The text also says to limit the output to between 0.1 and 0.9. A couple of questions:
1) I used the LTSpice voltage dependent voltage source, put the output of the compensator into the component and set the scale factor to 0.5. Does this work?

2) Where do the limit values 0.1 and 0.9 come from and how can they be implemented?

Thanks.

-Drew