Rainbow Electronics DS3134 - Manual (Page 149)

DS3134
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PCI Target Retry
Targets can terminate the requested bus transaction before any data is transferred because the target is
busy and temporarily unable to process the transaction. Such a termination is called a target retry and no
data is transferred. A target retry is signaled to the initiator by the assertion of PSTOP* and not asserting
PTRDY* on the initial data phase (see Figure 9.1F). When Chateau is a target, it will only issue a target
retry when the Host is accessing the Local Bus. This will occur when the Local Bus is being operated in
the arbitration mode and at the instant the Host requests access to the Local Bus, it is busy. See Section
10.1 for more details on the operation of the Local Bus.
PCI Target Retry Figure 9.1F
PCI Target Disconnect
A target can terminate a transaction prematurely by asserting PSTOP* (see Figure 9.1G). Depending on
the current state of the ready signals when PSTOP* is asserted, data may or may not be transferred. The
target will always deassert PSTOP* when it detects that the initiator has deasserted PFRAME*. When
Chateau is a target, it will disconnect with data after the first data phase is complete if the master attempts
a burst transaction. This is because the device does not support burst transactions when it is a target.
When it is an initiator and experiences a disconnect from the target, it will attempt another bus transaction
(if it still has the bus granted) after waiting either one (disconnect without data) or two clock cycles
(disconnect with data).
1 2 3 4 5 6 7 8 9 10
PCLK
PFRAME*
PSTOP*
PDEVSEL*
pci_tret
PTRDY*
PIRDY*