Based on the below picture ,describing anti-collision procedure : If more than 1 PICC will be present in the reading field of the PCD ,they will be transmitted their ATQA in the same time in answer to the REQA and because of unity of IDs ,PCD will be received different ATQA(different bit of data) and collision will be occur. e.g.:

PICC1_UID=0b00000001
PICC2_UID=0c00000000

In this situation whats received data by PCD (from digital logical data point of view ?)and how PCD recognized collision in the received ATQA frame?