AD977 output format and conversion algorithm

I have a question about the ADC AD977. The output format can be straight binary or 2s complement (pin SB/BTC). I am using bipolar input signals (negative and positive voltages). When selecting 2s complement format, does that mean the successive approximation algorithm is done using 2s complement format "logic" or it's first converted with straight binary offset logic (e.g., 000=-V, 100=0 V and 111=+V) and the converted to 2s complement?  Thanks.