ADuC7026 ECLK

Hello,

According to ADuC7026 datasheet,

nRS signal rising time is specified 0-4ns delay than ECLK rising time.

But the customer measured nRS rising time is about 5ns faster than external Xtal (40MHz) rising time.

I would like to know:

Each ECLK on timing specifications are based on ECLK pin out?  (when using external Xtal like above 40MHz Xtal)

Thank you for your help in advance.

Best regards,

Sofy