
MOTOROLA
Chapter 8. Signal Descriptions
8-33
Signal Descriptions
8.3.7.1.3
Data Bus Out (core_dh_out[0:31], core_dl_out[0:31])—Output
The core also implements data bus output enable and data bus high-impedance enable
signals. core_dh_out[0:31] and core_dl_out[0:31] act as follows:
If core_d_tre is asserted, the outputs are in one of the following three states—high
impedance, driven high, or driven low.
If core_d_tre is negated, the outputs are either driven to the high or low state. In this
case, valid values on core_dh_out[0:31] and core_dl_out[0:31] exist when
core_d_oe is asserted.
Following are the state meaning and timing comments for core_dh_out[0:31] and
core_dl_out[0:31].
State Meaning
Asserted/Negated—Represent the state of data during a data write.
Byte lanes not selected for data transfer do not supply valid data.
Timing Comments
Assertion/Negation—Occurs one clock cycle after qualified data bus
grant (coincides with core_dbb_out).
High Impedance—Occurs on the bus clock cycle after core_ta is
asserted, after the negation of core_d_oe, if core_d_tre is asserted. If
core_d_tre is negated, core_dh_out[0:31] and core_dl_out[0:31] are
always driven.
8.3.7.1.4
Data Bus Output Enable (core_d_oe)—Output
core_d_oe is an output-enable indicator to its corresponding bus signals. Following are the
state meaning and timing comments for core_d_oe.
State Meaning
Asserted—Indicates that the core is driving a valid data and data
parity.
Negated—Indicates one of the following two conditions:
If core_d_tre is negated, negated core_d_oe indicates that the core is
not driving valid core_dh_out[0:31] and core_dl_out[0:31] values.
If core_d_tre is asserted, negated core_d_oe indicates that
core_dh_out[0:31] and core_dl_out[0:31] are in the high-impedance
state.
Timing Comments
Assertion/Negation—Occurs one clock cycle after qualified data bus
grant (coincides with core_dbb_out).
Note that negation of core_d_oe may force the data bus and data
attribute signals to the high-impedance state, if core_d_tre is
asserted.
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