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.
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...