The address sent out to the instruction memory is always a word address, access size is always a word (32 bits) and writes are not supported. Hence, byte enables and read/write qualifiers are not present for the instruction memory interface.
The CPU core asserts the memory request signal (active low, cpu_imem_enz_o) along with the corresponding address (cpu_imem_addr_o) until a ready (active high, cpu_imem_rdy_i) is received from the memory subsystem.
For a zero-wait state access, the ready is expected the next cycle to the request. Ready must be de-asserted to extend the access cycle for a higher wait state memory subsystem.
The CPU samples the read data bus (cpu_imem_rdata_i[31:0]) when ready is asserted.