PM7367 datasheet(308/323 Pages) PMC

308 / 323 page

PM7367 FREEDM-32P32

DATA SHEET

PMC-1991499

ISSUE 2

FRAME ENGINE AND DATA LINK MANAGER

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE

294

Figure 34 – PCI Exclusive Lock Cycle

PCICLK

FRAMEB

AD[31:0]

678

TRDYB

DEVSELB

Address

Data

IRDYB

LOCKB

Address

Data

Fast back-to-back transactions are used by an initiator to conduct two

consecutive transactions on the PCI bus without the required idle cycle between

them. This can only occur if there is a guarantee that there will be no contention

between the initiator or targets involved in the two transactions. In the first case,

an initiator may perform fast back-to-back transactions if the first transaction is a

write and the second transaction is to the same target. All targets must be able

to decode the above transaction. In the second case, all of the targets on the

PCI bus support fast back-to-back transactions, as indicated in the PCI Status

configuration register. The FREEDM-32P32 only supports the first type of fast

back-to-back transactions and is shown in Figure 35.

During clock 1, the initiator drives FRAMEB to indicate the start of a cycle. It also

drives the address onto the AD[31:0] bus and drives the C/BEB[3:0] lines with

the write command. In this example the command would indicate a single write.

The IRDYB, TRDYB and DEVSELB signals are in turnaround mode and are not

being driven for this clock cycle. This cycle on the PCI bus is called the address

phase.

During clock 2, the initiator ceases to drive the address onto the AD[31:0] bus

and starts driving the data element. The initiator also drives the C/BEB[3:0] lines

with the byte enables for the write data. IRDYB is driven active by the initiator to

indicate that the data is valid.

The initiator negates FRAMEB since this the last data phase of this cycle. The

target claims the transaction by driving DEVSELB active and drives TRDYB to

indicate to the initiator that it is ready to accept the data.

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