A strange question in drc check.

Hello everyone,

I'm running one drc check with dracula but worried by a strange question.

The layout view is simple, which including one HV polygon and diffusion one.
There're some external separation and enclosing violations in the view. The
following is the part of the rule file:

;************************************
; *** HV Layer ***
;************************************
ENC[TO] DIFF HV LT 1.2 OUTPUT E3AH 45
EXT[TO] HV DIFF LT 1.2 OUTPUT E3BH 45
ENC[TO] PO1 HV LT 0.8 OUTPUT E3CLH 45
;
;***********************************
; *** PO1 Layer ***
;***********************************
WIDTH PO1 LT 0.8 OUTPUT E4ALH 45
EXT[H] PO1 LT 1.2 OUTPUT E4BLH 45
EXT[TO] PO1 DIFF LT 0.8 OUTPUT E4CLH 45
;

The purpose is to check out those violations. But the above rule cannot do
it, unless I do any item in these modification:
1. Add one poly1 polygon in the layout view;
2. Comment the line 'ENC[TO] PO1 HV LT 0.8 OUTPUT E3CLH 45'
3. Comment the line 'WIDTH PO1 LT 0.8 OUTPUT E4ALH 45'
4. Comment the line 'EXT[H] PO1 LT 1.2 OUTPUT E4BLH 45'

Since layer 'HV', 'PO1' and 'DIFF' are all original layer, layer 'PO1'
should not have more effection to rule E3AH45 and E3BH45, but I have no way
to understand the above behavior. Who may kindly give me some advice?

BTW, I've tried to convert the rule file to calibre format without any other
modification, calibre can sign out the errors.

Thanks for your help!

B.R.

Joffre