Chapter 2. Signal Descriptions and Clocking
2-13
Detailed Signal Descriptions
cycle when it cannot provide valid data to the target. During a read,
the MPC8240 negates IRDY to insert a wait cycle when it cannot
accept data from the target.
2.2.1.8.2 Initiator Ready (IRDY)—Input
Following is the state meaning for IRDY as an input signal.
State Meaning
Asserted—Indicates another PCI master is able to complete the
current data phase of a transaction.
Negated—If FRAME is asserted, it indicates a wait cycle from
another master. This is used by the MPC8240 to insert wait cycles
when it is a target of a PCI transaction. If FRAME is negated, it
indicates the PCI bus is idle.
2.2.1.9 Lock (LOCK)—Input
The lock (LOCK) signal is an input on the MPC8240. See Section 7.5, “Exclusive Access,”
for more information. Following is the state meaning for the LOCK input signal.
State Meaning
Asserted—Indicates that a master is requesting exclusive access to
memory, which may require multiple transactions to complete.
Negated—Indicates that a normal operation is occurring on the bus,
or an access to a locked target is occurring.
2.2.1.10 Target Ready (TRDY)
The target ready (TRDY) signal is both an input and output signal on the MPC8240.
2.2.1.10.1 Target Ready (TRDY)—Output
Following is the state meaning for TRDY as an output signal.
State Meaning
Asserted—Indicates that the MPC8240, acting as a PCI target, can
complete the current data phase of a PCI transaction. During a read,
the MPC8240 asserts TRDY to indicate that valid data is present on
AD[31:0]. During a write, the MPC8240 asserts TRDY to indicate
that it is prepared to accept data.
Negated—Indicates that the PCI initiator needs to wait before the
MPC8240, acting as a PCI target, can complete the current data
phase. During a read, the MPC8240 negates TRDY to insert a wait
cycle when it cannot provide valid data to the initiator. During a
write, the MPC8240 negates TRDY to insert a wait cycle when it
cannot accept data from the initiator.
Содержание MPC8240
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Страница 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Страница 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Страница 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Страница 516: ...16 14 Watchpoint Trigger Applications ...
Страница 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
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Страница 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...