simulink model of pipelined adc

i have downloaded one simulink model file of pipelined adc from "file exchange". but i have some questions regarding the same. 1. u have used 5 bit and 4 bit subadc but only one output bit is coming out from each subadc. 2. what's the purpose of summation unit used after subadc. 3. which type of representation has used for negative numbers like signed or 2's complement. and is there any special unit is required for particular representation. 4. how can i give particular input voltage only like -1v, 0v,0.5v only to output response. 5. which type of subadcs has used like 1 bit, 1.5 bit or anyone else. 6. i i have to do calibration, when should i do before digital error correction logic or after that block. pls help me to solve my problems.