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.