As an example, let M[$42]=$80, M[$43]=$10 and Y=$F1.
The instruction LDA ($42),Y will execute as follow, with phi2 ϕ2 as the first half-cycle and phi1 ϕ1 as the second half-cycle:
*T0: Fetch opcode $B1 (LDA (zp),Y) from memory then increment PC
*T1: Fetch operand byte $42 (zero page pointer address) then increment PC