
MOTOROLA
Chapter 8. Signal Descriptions
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Signal Descriptions
State Meaning
Asserted—Indicates (for a write transaction) that the core must
release the data bus and the data bus parity signals to high impedance
during the following cycle. The data tenure remains active,
core_dbb_out remains driven, and the transfer termination signals
are still monitored by the core.
Negated—Indicates the data bus should remain normally driven.
core_dbdis is ignored during read transactions.
Assertion/Negation—May be asserted on any clock cycle when the
core is driving, or will be driving the data bus; may remain asserted
for multiple cycles.
Timing Comments
8.3.8
Data Transfer Termination Signals
Data termination signals are required after each data beat in a data transfer. Note that in a
single-beat transaction, the data termination signals also indicate the end of the tenure.
While in burst accesses, the data termination signals apply to individual beats and indicate
the end of the tenure only after the final data beat.
For a detailed description of how these signals interact, see Section 9.4.4, “Data Transfer
Termination.”
8.3.8.1
Transfer Acknowledge (core_ta)—Input
Following are the state meaning and timing comments for the core_ta input.
State Meaning
Asserted—Indicates that a single-beat data transfer completed
successfully or that a data beat in a burst transfer completed
successfully (unless core_drtry is asserted on the next bus clock
cycle).
Note that core_ta must be asserted for each data beat in a burst
transaction, and must be asserted during assertion of core_drtry. For
more information, see Section 9.4.4, “Data Transfer Termination.”
Negated—(During assertion of core_dbb_out) indicates that, until
core_ta is asserted, the core must continue to drive the data for the
current write or must wait to sample the data for reads.
Timing Comments
Assertion—Must not occur before core_aack for the current
transaction (if the address retry mechanism is to be used to prevent
invalid data from being used by the processor); otherwise, assertion
may occur at any time during the assertion of core_dbb_out. The
system can withhold assertion of core_ta to indicate that the core
should insert wait states to extend the duration of the data beat.
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