Rows are connected to Port lines directly from where it will receive the cathode values. In other words, the dot which has to glow, its row pin should receive a logic '0' from the Microcontroller. The columns are connected to anodes, therefore the line which is to be glown should receive logic '1' from the shift register, which in turn will receive logic '1' from the Microcontroller on it's SI pin and a +ve edge on the CLK pin of the shift register.
