OR3LP26B datasheet(53/184 Pages) AGERE

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Lucent Technologies Inc.

Data Sheet

ORCA OR3LP26B FPSC

March 2000

Embedded Master/Target PCI Interface

Lucent Technologies Inc.

PCI Bus Core Detailed Description Dual Port (continued)

Target Write I/O, Delayed Transaction

Figure 11 (PCI bus) and Figure 13 (FPGA bus) show the timing for a Target I/O write operation that is handled as a

delayed transaction; that is, the operation completes on the local (FPGA) bus before completing on the PCI bus.

The FPGA application indicates its desire to do this by asserting signal deltrn. In Figure 11, three transactions are

shown: the first is the initial write that latches the command, address, data, and byte enables in the PCI core. The

core's Target logic then issues a retry, obligating the remote Master to continue to issue that identical request until

data is moved. Meanwhile, the information is relayed to the FPGA interface via the address and data FIFOs, trig-

gering the FPGA interface exchange discussed below and shown in Figure 13. All subsequent read or write

requests to memory, I/O, or configuration space will result in retries, as shown in the second transaction of Figure

11. The third transaction is the final transaction that completes the transfer of data. Although the data was actually

latched and forwarded to the FPGA from the first transaction, it is not until the FPGA acknowledges that it has

received the data, by emptying the Target write FIFO, that the PCI core acknowledges to the remote Master that it

has received the data by performing a disconnect with data. The timing on this third transaction is identical to the

timing of the first except that trdyn accompanies stopn to indicate the disconnect with data.

The timing on the FPGA interface (Figure 13) shows that the first indication to the FPGA application that a new

operation has begun is the assertion of target request (treqn), together with the new command on bus

datatofpga. The FPGA application responds by asserting target address enable (taenn) and accepting the com-

mand and subsequent address on bus datatofpga. This is followed by deassertion of taenn, assertion of Target

write data enable (twdataenn), and the receiving of the data on bus datatofpga. Although only 32 bits of data are

being transferred, the FPGA application must accept 64 bits of data (two clock cycles) because the FIFOs are

operating in 64-bit mode.

5-7372(F).a

Figure 11. Target I/O Write, Delayed (PCI Bus, 64-Bit)

Ta0

Ta1

Ta2

Ta3

Ta4

Ta5

Ta6

Tb0

Tb1

Tb2

Tb3

Tb4

Tb5

Tb6

Tc0

Tc1

Tc2

Tc3

Tc4

Tc5

Tc6

ADRS

DATA

ADRS

DATA

ADRS

DATA

CMD

BEs

CMD

BEs

CMD

BEs

clk

framen

ad[31:0]

c/be[3:0]n

irdyn

devseln

trdyn

stopn

TRANSACTION #1: ADDRESS, BYTE ENABLES,

COMMAND, AND WRITE DATA LATCHED AS A

DELAYED WRITE REQUEST.

TRANSACTION #2: DISCONNECTED W/O DATA

BECAUSE WRITE COMPLETION NOT RECEIVED.

TRANSACTION #3: DISCONNECTED WITH DATA

BECAUSE WRITE COMPLETION RECEIVED.

OR3LP26B Datasheet(PDF) 53 Page - Agere Systems

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