Wednesday, February 5, 2014

An old ARM clocking scheme

An interesting fact about the old ARM clocking scheme, ((c) ARM System on chip architecture )

Unlike the MU0 example presented in Section 1.3 on page 7, most ARMs do not
operate with edge-sensitive registers; instead the design is based around 2-phase
non-overlapping clocks, as shown in Figure 4.8, which are generated internally from
a single input clock signal. This scheme allows the use of level-sensitive transparent
latches. Data movement is controlled by passing the data alternately through latches
which are open during phase 1 and latches which are open during phase 2. The
non-overlapping property of the phase 1 and phase 2 clocks ensures that there are
no race conditions in the circuit.

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