A fast analog trigger processor is being developed for the measurement
of the parity violating asymmetry of the cross section of elastically
scattered polarized electrons on unpolarized protons. The total event
rate expected is about 100 MHz in the whole detector which consists o
f 1022 PbF2 crystals. This requires fast cluster recognition, spatial
and temporal pile-up rejection and fast data storage. First results of
a prototype are discussed.