How to explain the ablatives uppādā and anuppādā?

Dear Pali Friends,

Uppādā vā, bhikkhave, tathāgatānaṃ anuppādā vā tathāgatānaṃ, ṭhitāva sā dhātu dhammaṭṭhitatā dhammaniyāmatā. Sabbe saṅkhārā aniccā.

This is a famous passage with which you all must be familiar. It is always translated along the lines of "whether there is the arising of Tathagatas or no arising of Tathagatas, that element (principle) stands ... All conditioned things are impermanent."

My question concerns the ablatives uppādā and anuppādā. I consulted several grammars in search of an explanation of the ablative that fits the usage here, but did not succeed in finding one. I skimmed Wijesekera's book on the Pali cases, too, but did not find a fitting explanation of this ablative. It is obviously not the ablative of separation or the ablative of causation. So what aspect of the ablative is involved here? Are there other examples of the ablative used in this way?

Thank you in advance,

-- 
Ven. Bhikkhu Bodhi
Chuang Yen Monastery
2020 Route 301
Carmel NY 10512
U.S.A.

Sabbe sattā averā hontu, abyāpajjā hontu, anighā hontu, sukhī hontu!
願眾生無怨，願眾生無害，願眾生無惱，願眾生快樂！
May all beings be free from enmity, free from affliction, free from distress. May they be happy!