  This paper describes the measurements of energy and time response and
resolution of a 3 x 3 array made of undoped CsI crystals coupled to large area
Hamamatsu Multi Pixel Photon Counters. The measurements have been performed
using the electron beam of the Beam Test Facility in Frascati (Rome, Italy) in
the energy range 80-120 MeV. The measured energy resolution, estimated with the
FWHM, at 100 MeV is 16.4%. This resolution is dominated by the energy leakage
due to the small dimensions of the prototype. The time is reconstructed by
fitting the leading edge of the digitized signals and applying a digital
constant fraction discrimination technique. A time resolution of about 110 ps
at 100 MeV is achieved.
