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A storage clock provides the neces-
sa~
timing pulses and gates to operate
the storage unit on a cycle-by-cycle
basis.
This clock is started by the
read or write signal form the
cpu.
Once
started, it operates for a complete read
or write cycle.
For example, suppose a position is to
be read out, the byte of information
thus obtained is to be used in a compu-
tation, and the result of the computa-
tion is to
be
placed back into the same
storage position.
The CPU specifies a
storage location by placing a storage
address in the MN-register.
The storage
circuitry is signaled to read and the
storage clock is started (Figure 2-54).
A storage read cycle results, during
which time the desired storage location
is read out, and the resulting byte is
placed in the CPU R-register.
The CPU
then makes the necessary computation and
places the result back into the R-
register.
Once again, the storage unit
clock is started.
This time, however,
the storage unit is signaled to write.
A storage write cycle results, during
which time the byte from the R-register
is written into the addressed storage
position.
In each case (read and
write), the clock operated for a
complete cycle once it had been started.
2-43
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