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PI7C7100
3-Port PCI Bridge
ADVANCE INFORMATION
After PI7C7100 makes 2
24
(default) attempts of the same delayed read transaction on the target bus, PI7C7100 asserts
P_SERR# if the primary SERR# enable bit is set (bit 8 of command register for secondary bus S1 or S2) and the delayed-
write-non-delivery bit is not set. The delayed-write-non-delivery bit is bit 5 of P_SERR# event disable register (offset 64h).
PI7C7100 will report system error. See Section 7.4 for a description of system error conditions.
4.8.4 Target Termination Initiated by PI7C7100
PI7C7100 can return a target retry, target disconnect, or target abort to an initiator for reasons other than detection of that
condition at the target interface.
4.8.4.1 Target Retry
PI7C7100 returns a target retry to the initiator when it cannot accept write data or return read data as a result of internal
conditions. PI7C7100 returns a target retry to an initiator when any of the following conditions is met:
For delayed write transactions:
• The transaction is being entered into the delayed transaction queue.
• Transaction has already been entered into delayed transaction queue, but target response has not yet been
received.
• Target response has been received but has not progressed to the head of the return queue.
• The delayed transaction queue is full, and the transaction cannot be queued.
• A transaction with the same address and command has been queued.
• A locked sequence is being propagated across PI7C7100, and the write transaction is not a locked transaction.
• The target bus is locked and the write transaction is a locked transaction.
• Use more than 16 clocks to accept this transaction.
For delayed read transactions:
• The transaction is being entered into the delayed transaction queue.
• The read request has already been queued, but read data is not yet available.
• Data has been read from target, but it is not yet at head of the read data queue, or a posted write transaction
precedes it.
• The delayed transaction queue is full, and the transaction cannot be queued.
• A delayed read request with the same address and bus command has already been queued.
• A locked sequence is being propagated across PI7C7100, and the read transaction is not a locked transaction.
• PI7C7100 is currently discarding previously pre-fetched read data.
• The target bus is locked and the write transaction is a locked transaction.
• Use more than 16 clocks to accept this transaction.
For posted write transactions:
• The posted write data buffer does not have enough space for address and at least one DWORD of write data.
• A locked sequence is being propagated across PI7C7100, and the write transaction is not a locked transaction.
When a target retry is returned to the initiator of a delayed transaction, the initiator must repeat the transaction with the
same address and bus command as well as the data if it is a write transaction, within the time frame specified by the master
timeout value. Otherwise, the transaction is discarded from the buffers.