Chapter 7. PCI Bus Interface
7-17
PCI Bus Transactions
Figure 7-6. PCI Burst Write Transaction
7.4.3 Transaction Termination
A PCI transaction may be terminated by either the initiator or the target. The initiator is
ultimately responsible for concluding all transactions, regardless of the cause of the
termination. All transactions are concluded when FRAME and IRDY are both negated,
indicating the bus is idle.
7.4.3.1 Master-Initiated Termination
Normally, a master initiates termination by negating FRAME and asserting IRDY. This
indicates to the target that the final data phase is in progress. The final data transfer occurs
when both TRDY and IRDY are asserted. The transaction is considered complete when data
is transferred in the last data phase. After the final data phase, both FRAME and IRDY are
negated (the bus becomes idle).
There are three types of master-initiated termination:
•
Completion—Refers to termination when the initiator has concluded its intended
transaction. This is the most common reason for termination.
•
Timeout—Refers to termination when the initiator loses its bus grant (GNTn is
negated), and its internal latency timer has expired. The intended transaction is not
necessarily concluded.
•
Master-abort—An abnormal case of master-initiated termination. If no device
(including the subtractive decoding agent) asserts DEVSEL to claim a transaction,
the initiator terminates the transaction with a master-abort. For a master-abort
termination, the initiator negates FRAME and then negates IRDY on the next clock.
If a transaction is terminated by master-abort (except for a special-cycle command),
the received master-abort bit (bit 13) of the PCI status register is set.
PCI_SYNC_IN
FRAME
IRDY
AD[0:31]
ADDR
DEVSEL
TRDY
C/BE[0:3]
DATA4
DATA1
DATA2
DATA3
Byte enables 1 Byte enables 2
CMD
BEs 4
Byte enables 3
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 ...