Visual format - Length Restriction problem

System

I have a problem while using Visual format as an external editor in my code.

Below given is the snippet from code from one of the datacapture.cfg file that I have written
<item name='Asset_Long_Desc1'>
<label>Content Summary Text</label>
<description>Enter the summary text (1) for the content</description>
<database deploy-column='t' searchable='t' />
<textarea external-editor='visualformat' rows='8' cols='50' maxlength='512' required='f' external-editor-config='lillyconnect.xml' />

I have mentioned maxlength for the text area as 512 chars . But I am able to key in more that 512 Characters. It seems that Visual format is not restricting the length of text area to 512 chars.
Is there any way I can restrict the length to 512 chars . Is there any simple way to do that or Shall I have to use form APT to do the same.


Please help.