Driving Multiple LEDs with the Help of Shift Register
The shift register and output register can be updated separately. There is a bit clock signal (SRCK) for loading serial data bits into the shift register and separate load clock signal (RCK) to transfer the shift register contents to output latches. So no matter how slowly the shift register contents are updated and bit patterns shifted to correct positions, all 8 output bits get updated simultaneously when the output register is loaded. So it is possible to change one output bit without having glitches on other outputs, as the shift register is not directly driving the pins.