
8-28
G2 PowerPC Core Reference Manual
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MOTOROLA
Signal Descriptions
High Impedance—Indicates that the core does not need the snooped
address tenure to be retired. Occurs two bus cycles after core_aack is
asserted, after the negation of core_artry_oe, if core_artry_tre is
asserted. If core_artry_tre is negated, core_artry_out is always
driven.
8.3.5.2.3
Address Retry Output Enable (core_artry_oe)—Output
core_artry_oe is an output-enable indicator to its corresponding bus signals. Following are
the state meaning and timing comments for core_artry_oe.
State Meaning
Asserted—Indicates that the G2 core is driving a valid
core_artry_out.
Negated—Indicates one of the following two conditions:
If core_artry_tre is negated, negated core_artry_oe indicates that the
core is not driving a valid core_artry_out value.
If core_artry_tre is asserted, negated core_artry_oe indicates that
core_artry_out is in the high-impedance state.
Timing Comments
Assertion—Asserted the second bus cycle following the assertion of
core_ts_in if a retry is required and it remains asserted until one bus
cycle after core_aack is asserted.
Negation—Occurs the second bus cycle after the assertion of
core_aack and remains asserted for a minimum of one-half bus cycle
(depends on clock mode) before it is negated for one bus cycle.
Note that negation of core_artry_oe may force core_artry_out to the
high-impedance state, if core_artry_tre is asserted.
8.3.5.2.4
Address Retry High-Impedance Enable (core_artry_tre)—Input
Following are the state meaning and timing comments for core_artry_tre. core_artry_tre is
a high-impedance enable signal on the G2 core and can be used to create an external
bidirectional core_artry signal. When the related input/output signals (core_artry_in and
core_artry_out) are wire-ORed together, the resulting signal functions similar to a
bidirectional 60x bus signal when core_artry_tre is asserted. See Section 8.2.2.2, “Logic
Gate Equivalent and Bidirectional Signals,” for more information.
State Meaning
Asserted—core_artry_oe controls whether core_artry_out is driven
or forced to a high-impedance state.
Negated—Indicates core_artry_out is always driven.
Timing Comments
Assertion/Negation—Must be set up prior to negation of the
core_hreset signal and remain stable during core operation. This is a
static configuration.
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