can fall on a syllable that is designated as a weak syllable in the standard, unvaried iambic pentameter pattern. In the Donne line, the word God is not a maximum. That is because it is followed by a pause. Similarly the words you, mend, and bend are not maxima since they are each at the end of a line (as required for the rhyming of mend/bend and you/new.) Rewriting the Donne quatrain showing the stress maxima (denoted with an "M") results in the following:

 /  ×   ×  M       ×   M  ×     /    ×   /Batter my heart three-personed God, for you×   M   ×    /      ×        /   ×    M    ×  /As yet but knock, breathe, shine and seek to mend.  ×  /  ×   M   ×     /   ×      /   ×(×)   /That I may rise and stand o'erthrow me and bend ×    M     ×   /      ×    /   ×    M    ×  /Your force to break, blow, burn and make me new.