CS5920 datasheet(122/160 Pages) AMCC

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S5920 – PCI Product

Revision 1.01 – November 28, 2005

AMCC Confidential and Proprietary

DS1596

122

Data Book

address phase followed by a single data phase. If the

S5920 determines that the address is within one of its

defined Pass-Thru regions, it indicates to the Add-On

a write to the Pass-Thru Data Register (APTD) is

required.

Figure 6 shows a Passive Mode single cycle Pass-

Thru read access (Add-On write) using PTADR#. The

Add-On reads data from a source on the Add-On and

writes it to the APTD register.

Figure 64. PCI To Add-On Passive Read

Clock 0:

The address is recognized as a PCI read of

Pass-Thru region 2. The PCI bus read address is

stored in the Pass-Thru Address Register. 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 a Pass-Thru access is

pending.

PTBURST# Deasserted. The access has a single data

phase.

PTNUM[1:0] 2h. Indicates the access is to Pass-Thru

region 2.

PTWR Deasserted. The Pass-Thru access is a read.

PTBE[3:0]# 0h. Indicates the Pass-Thru access has all

bytes valid.

Clock 2:

The PTADR# input is asserted to read the

Pass-Thru Address Register. The address can be

latched on the next rising-edge of ADCLK.

Clock 3:

This turn-around cycle is required to avoid

contention on the DQ bus. Time must be allowed after

PTADR# is deasserted for the DQ outputs to float

before add-on logic attempts to write to the Pass-Thru

Read FIFO.

Clock 4:

WR#, SELECT#, BE[3:0]#, and ADR[6:2] are

asserted to write to the Pass-Thru Read FIFO at

address 2Ch. The Add-On logic drives the DQ bus

with the requested data. PTRDY# is also asserted,

indicating that the Add-On is finished with the transfer.

Clock 5:

The data on the DQ bus is latched into the

Pass-Thru Read FIFO. As the S5920 samples

PTRDY# asserted, PTATN# is deasserted and the

Pass-Thru access is complete. PTBE[3:0] will update

one clock after WR# is asserted to indicate which

bytes have not yet been read. If add-on logic requires

more time to provide data (slower memory or peripher-

als), PTRDY# can be delayed, extending the cycle.

Clock 6:

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).

PCI to Pass-Thru Burst Writes

A PCI to Pass-Thru burst write operation occurs when

a PCI initiator writes multiple values to a Pass-Thru

region. A PCI burst cycle consists of an address phase

followed by multiple data phases. If the S5920 deter-

mines that the requested address is within one of its

defined Pass-Thru regions, the initial PCI address is

stored into the Pass-Thru Address Register (APTA).

The data from each data-cycle is individually latched

into the Pass-Thru Data register (APTD) or Pass-Thru

Write FIFO.

ADCLK

PTATN#

PTBURST#

PTNUM[1:0]

PTWR

PTBE[3:0]

SELECT#

ADR[6:2]

BE[3:0]#

WR#

DQ[31:0]

PTRDY#

2Ch

DATA

ADDR

PTADR#

012

CS5920 数据表(PDF) 122 Page - Applied Micro Circuits Corporation

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