
MOTOROLA
Chapter 9. Core Interface Operation
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9-25
Data Bus Tenure
An assertion of core_artry_in causes the data tenure to be terminated immediately if
core_artry_in is for the address tenure associated with the data tenure in operation. If
core_artry_out is connected for the G2 core, the earliest allowable assertion of core_ta to
the core is directly dependent on the earliest possible assertion of core_artry_in to the G2
core; see Section 9.3.3, “Address Transfer Termination.”
If the G2 core clock is configured for 1:1 or 1.5:1 (processor clock to bus clock ratio) mode
and the core is performing a burst read into its data cache, at least one wait state must be
provided between the assertion of core_ts and the first assertion of core_ta for that
transaction. If no-core_drtry mode is also selected, at least two wait states must be
provided. The wait states are required due to possible resource contention in the data cache
caused by a block replacement (or cast-out) required in connection with the new linefill.
These wait states may be provided by withholding the assertion of core_ta to the G2 core
for that data tenure, or by withholding core_dbg to the core, thereby delaying the start of
the data tenure. This restriction applies only to burst reads into the data cache when
configured in 1:1 or 1.5:1 clock modes. (It does not apply to instruction fetches, write
operations, noncachable read operations, or non-1:1 or non-1.5:1 clock modes.)
9.4.4.1
Normal Single-Beat Termination
Normal termination of a single-beat data read operation occurs when core_ta is asserted by
a responding slave. The core_tea and core_drtry signals must remain negated during the
transfer (see Figure 9-8).
Figure 9-8. Normal Single-Beat Read Termination
core_ts_out
qual_dbg
core_dbb_out
Data
core_ta_in
core_drtry
core_aack
Bus Clock
0
1
2
3
4
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