approach, so in the first instance, we could use mouse keys or spe-
cific keys on the keyboard to initiate a record sequence, or play-
back, or store, but ultimately, depending on how complex we wish
to make the design, it would be possible to design a simple user
interface with buttons or similar user interface features, actually
on the display to allow controls to drive the system.
Specifying the interfaces
From the sketch shown in Figure 11 we can begin to identify the
interface requirements for the top level design. First we clearly
need a clock and reset (active low), so keeping things simple
(always a good strategy) we can define the clock pin as ...