DS3134 datasheet(149/203 Pages) DALLAS

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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).

1234

5678910

PCLK

PFRAME*

PSTOP*

PDEVSEL*

pci_tret

PTRDY*

PIRDY*

DS3134 Datasheet(PDF) 149 Page - Dallas Semiconductor