CS5920 datasheet(121/160 Pages) AMCC

121 / 160 page

S5920 – PCI Product

Revision 1.01 – November 28, 2005

AMCC Confidential and Proprietary

DS1596

121

Data Book

Figure 62. PCI To Add-On Passive Write

Figure 63. PCI To Add-On Passive Write w/Pass-Thru

Address

Clock 0: The address is recognized as a PCI write to

Pass-Thru region 1. The PCI bus write address is

stored in the Pass-Thru Address Register. The PCI

bus write data is stored in the S5920 Write FIFO. Add-

On bus signals PTATN#, PTBURST#, PTNUM[1:0],

PTWR and PTBE[3:0] will update on the next rising

edge of ADCLK.

Clock 1:

Pass-Thru signals PTATN#, PTBURST#,

PTNUM[1:0], PTWR and PTBE[3:0] are driven to indi-

cate what action is required by Add-On logic. These

status signals are valid only when PTATN# is active.

Add-On logic can decode status signals upon the

assertion of PTATN#.

PTATN# Asserted. Indicates Pass-Thru access is

pending.

PTBURST# Not asserted. The access has a single

data phase.

PTNUM[1:0] 1h. Indicates the access is to Pass-Thru

region 1.

PTWR Asserted. The Pass-Thru access is a write.

PTBE[3:0]# 0h. Indicate the Pass-Thru has all bytes

valid.

Clock 2:

The PTADR# input is asserted to read the

Pass-Thru Address Register. The assertion of

PTADR# will immediately cause the address to be

driven on the DQ bus. RD#, SELECT#, byte enable,

and the address inputs are asserted to read the Pass-

Thru Data Register at offset 2Ch. DQ[31:0] is driven

one clock after RD# and SELECT# are asserted.

Asserting PTADR# and RD# at the same time will save

a clock cycle, since the assertion of the RD# won’t

cause the data to be driven until a clock later. The

Add-On also asserts PTRDY#, indicating that the cur-

rent transfer is complete.

Clock 3:

PTBE[3:0] are updated to indicate which

bytes have not yet been read. Data is driven on the

DQ bus because RD# was asserted a clock earlier.

The Add-On logic reads the data and deasserts

PTRDY#. As PT RD Y# was sampled asserted,

PTATN# is immediately deasserted and the Pass-Thru

access is completed with the next clock. If add-on

logic requires more time to read the Pass-Thru Data

can be delayed, extending the cycle.

Clock 4:

As PTATN# is deasserted, the Pass-Thru

access is complete, and the S5920 can accept new

Pass-Thru accesses starting on the next clock. The

other Pass-Thru signals can also change (in anticipa-

tion of a new transfer). The S5920 stops driving the

DQ bus as RD# and SELECT# were not valid on the

previous cycle.

Single-Cycle PCI to Pass-Thru Read

A single-cycle PCI to Pass-Thru read operation occurs

when a PCI initiator reads a single value from a Pass-

Thru region. PCI single cycle transfers consists of an

ADCLK

PTATN#

PTBURST#

PTNUM[1:0]

PTWR

PTBE[3:0]

SELECT#

ADR[6:2]

BE[3:0]#

RD#

DQ[31:0]

PTRDY#

2Ch

PTDATA

ADCLK

PTATN#

PTBURST#

PTNUM[1:0]

PTWR

PTBE[3:0]

SELECT#

ADR[6:2]

BE[3:0]#

RD#

DQ[31:0]

PTADR#

DATA

ADDR

PTRDY#

2Ch

CS5920 Datasheet(PDF) 121 Page - Applied Micro Circuits Corporation

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