Chapter 7. PCI Bus Interface
7-15
PCI Bus Transactions
AD[31:0] as data signals. The turnaround cycle is enforced by the target with the TRDY
signal. The target provides valid data at the earliest one cycle after the turnaround cycle.
The target must drive the AD[31:0] signals when DEVSEL is asserted.
During the data phase, the C/BE[3:0] signals indicate which byte lanes are involved in the
current data phase. A data phase may consist of a data transfer and wait cycles. The
C/BE[3:0] signals remain actively driven for both reads and writes from the first clock of
the data phase through the end of the transaction.
A data phase completes when data is transferred, which occurs when both IRDY and TRDY
are asserted on the same clock edge. When either IRDY or TRDY is negated, a wait cycle
is inserted and no data is transferred. The initiator indicates the last data phase by negating
FRAME when IRDY is asserted. The transaction is considered complete when data is
transferred in the last data phase.
Figure 7-3 illustrates a PCI single-beat read transaction. Figure 7-4 illustrates a PCI burst
read transaction.
Figure 7-3. PCI Single-Beat Read Transaction
PCI_SYNC_IN
FRAME
IRDY
AD[31:0]
ADDR
DEVSEL
TRDY
C/BE[3:0]
Byte enables
CMD
DATA
Содержание MPC8240
Страница 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Страница 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Страница 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Страница 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Страница 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Страница 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Страница 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
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 ...
Страница 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Страница 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...