Internally, multiple numbers of this system clock oscillation are used for various purposes. If we desig-
nate each complete oscillation of the external crystal or clock source as a pulse, then two such pulses produce
a state. Six states generate one machine cycle. Instructions need one, two or four such machine cycles for
fetching the opcode and its execution (Fig. 2.11).
We have previously been introduced to the ALE signal of XX51. Two pulses of this ALE signal are
available for each machine cycle. A quick method to check whether an XX51 is functioning properly or not is
to monitor this ALE signal through an oscilloscope ...
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