Control Signals
There are two control signals and one special (ALE) in this category. All these signals are output signals.
RD (Read signal ) it is an active low control signal. It goes low when read operations reading from memory input output port takes place.
WR write signal it is also an active low control signal. It goes low when write operation writing into memory output takes place.
ALE address latch enable signal - it is an active high signal. It goes during first clock cycle and enable the latch used to de multiplex address bus from data bus. De multiplexing address and data bus is explained later in this chapter.