The ABCD3TA readout chip for silicon strip detectors of the ATLAS SemiConductor Tracker (SCT) is described. It is the final design of the single chip implementation of the binary readout architecture. The chip is manufactured in the DMILL radiation-hardened BiCMOS process. Summary of results of irradiations of ABCD3TA chips with up to 100 kGy and 2/spl times/10/sup 14/ n/cm/sup 2/ (1-MeV neutron NIEL equivalent) done with various sources is given in this paper. Measurements of single event effects with high-energy proton and pion beams are also reported. The tests proved that the chips are sufficiently radiation hard for application in the ATLAS SCT.