PI7C7300ANAE Pericom Semiconductor, PI7C7300ANAE Datasheet - Page 29

• Manufacturer Part Number: PI7C7300ANAE
• Description: IC PCI-PCI BRIDGE 3PORT 272-BGA
• Manufacturer: Pericom Semiconductor

Specifications of PI7C7300ANAE

• Applications: *
• Interface: *
• Voltage - Supply: *
• Package / Case: 272-PBGA
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PI7C7300A
3-PORT PCI-TO-PCI BRIDGE
ADVANCE INFORMATION
24
32
If PI7C7300A is unable to obtain read data from the target after 2
(default) or 2
(maximum) attempts, PI7C7300A will report a system error. The number of attempts is
programmable. PI7C7300A also asserts P_SERR# if the primary SERR# enable bit is set
in the command register. See Section 7.4 for information on the assertion of P_SERR#.
Once PI7C7300A receives DEVSEL# and TRDY# from the target, it transfers the data
read to the opposite direction read data queue, pointing toward the opposite inter-face,
before terminating the transaction. For example, read data in response to a downstream
read transaction initiated on the primary bus is placed in the upstream read data queue.
The PI7C7300A can accept one DWORD of read data each PCI clock cycle; that is, no
master wait states are inserted. The number of DWORD transferred during a delayed
read transaction depends on the conditions given in Table 4-5 (assuming no disconnect is
received from the target).
4.7.6
DELAYED READ COMPLETION ON INITIATOR BUS
When the transaction has been completed on the target bus, and the delayed read data is
at the head of the read data queue, and all ordering constraints with posted write
transactions have been satisfied, the PI7C7300A transfers the data to the initiator when
the initiator repeats the transaction. For memory read transactions, PI7C7300A aliases
the memory read, memory read line, and memory read multiple bus commands when
matching the bus command of the transaction to the bus command in the delayed
transaction queue. PI7C7300A returns a target disconnect along with the transfer of the
last DWORD of read data to the initiator. If PI7C7300A initiator terminates the
transaction before all read data has been transferred, the remaining read data left in data
buffers is discarded.
When the master repeats the transaction and starts transferring prefetchable read data
from data buffers while the read transaction on the target bus is still in progress and
before a read boundary is reached on the target bus, the read transaction starts operating
in flow-through mode. Because data is flowing through the data buffers from the target to
the initiator, long read bursts can then be sustained. In this case, the read transaction is
allowed to continue until the initiator terminates the trans-action, or until an aligned 4KB
address boundary is reached, or until the buffer fills, whichever comes first. When the
buffer empties, PI7C7300A reflects the stalled condition to the initiator by disconnecting
the initiator with data. The initiator may retry the transaction later if data are needed. If
the initiator does not need any more data, the initiator will not continue the disconnected
transaction. In this case, PI7C7300A will start the master timeout timer. The remaining
read data will be discarded after the master timeout timer expires. To provide better
latency, if there are any other pending data for other transactions in the RDB (Read Data
Buffer), the remaining read data will be discarded even though the master timeout timer
has not expired.
PI7C7300A implements a master timeout timer that starts counting when the delayed
read completion is at the head of the delayed transaction queue, and the read data is at the
head of the read data queue. The initial value of this timer is program-mable through
configuration register. If the initiator does not repeat the read transaction and before the
15
master timeout timer expires (2
default), PI7C7300A discards the read transaction and
read data from its queues. PI7C7300A also conditionally asserts P_SERR# (see Section
7.4).
Page 29 OF 109
09/25/03 Revision 1.09