Which bit of the byte written to a mapper register is taken into account first. For example, if I have the code

lda #$81
sta $FFFF

does it write a 1 to the array and then clear it all, or does it clear the array and write a 1 to bit zero afterwords? If I wanted, say, register 3 to have a value of %00011011, could I do this?

lda #$9B
sta $FFFF
lsr a
sta $FFFF
lsr a
sta $FFFF
lsr a
sta $FFFF
lsr a
sta $FFFF

or would I have to do a fifth shift and start with the value of %1011011x in the accumulator? Any explanation would be greatly appreciated. God bless you all.