  Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat has been a prolific
Gamma-Ray Burst (GRB) monitor. While the 2-pixel Compton scattered events (100
- 300 keV) are used to extract sensitive spectroscopic information, the
inclusion of the low-gain pixels (around 20% of the detector plane) after
careful calibration extends the energy range of Compton energy spectra to 600
keV. The new feature also allows single-pixel spectroscopy of the GRBs to the
sub-MeV range which is otherwise limited to 150 keV. We also introduced a new
noise rejection algorithm in the analysis ('Compton noise'). These new
additions not only enhances the spectroscopic sensitivity of CZTI, but the
sub-MeV spectroscopy will also allow proper characterization of the GRBs not
detected by Fermi. This article describes the methodology of single, Compton
event and veto spectroscopy in 100 - 600 keV for the GRBs detected in the first
year of operation. CZTI in last five years has detected around 20 bright GRBs.
The new methodologies, when applied on the spectral analysis for this large
sample of GRBs, has the potential to improve the results significantly and help
in better understanding the prompt emission mechanism.
