Sharepoint Foundation Can not update External List by Work Flow

Hi

I try to update External List by other list Work Flow, in Sharepoint 2010 Foundation.

Here is the manual： 

http://msdn.microsoft.com/en-us/library/office/ff394479(v=office.14).aspx

But it fails , and the error message is “The workflow could not update the item in the external data source. Make sure the user has permissions to access the external data source and update items.”

Is there some limited in Foundation?