A method and integrated circuit for accessing data in a pipelined data
processing apparatus in which the operating conditions of the pipelined
data processing apparatus are such that metastable signals may occur on
at least the boundaries of the pipelined stages is disclosed. The method
comprises the steps of: receiving an indication that an instruction is to
be processed by the pipelined data processing apparatus; generating a
memory access prediction signal, the memory access prediction signal
having a value indicative of whether or not the instruction is likely to
cause a read access from a memory; generating a predicted memory access
control value from the memory access prediction signal, the predicted
memory access control value being generated to achieve and maintain a
valid logic level for at least a sampling period thereby preventing any
metastability in the predicted memory access control value; and in the
event that the predicted memory access control value indicates that a
read access is likely to occur, causing a read access to be initiated
from the memory. Through this approach, an indication that an instruction
is to be processed by the pipelined data processing apparatus is received
and a memory access prediction signal indicative of whether or not the
instruction is likely to cause a read access from a memory is then
generated. The predicted memory access control signal is generated in a
way which prevents any metastability being present in that signal. Hence,
the signals used in a read access are prevented from being metastable
which removes the possibility that metastable signals are used directly
in the arbitration of data accesses. Also, the metastable signals may be
prevented from being propagated from stage to stage.