S5335 datasheet(140/189 Pages) AMCC

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S5335 – PCI Bus Controller, 3.3V

Revision 5.01 – November 30, 2005

AMCC Confidential and Proprietary

DS1657

140

Data Sheet

PASS-THRU OVERVIEW

The S5335 provides a simple registered access port to

the PCI bus. Using a handshaking protocol with Add-

On card logic, the PCI bus directly accesses resources

on the Add-On. The Pass-Thru data transfer method is

very useful for direct Add-On memory access, or

accessing registers within peripherals on an Add-On

board. Pass-Thru operation requires an external nv

memory boot device to define and configure the

S5335 Pass-Thru regions.

The S5335 provides four user-configurable Pass-Thru

regions. Each region corresponds to a PCI Configura-

tion Base Address Register (BADR1-4). A region

represents a block of address space (the block size is

user-defined). Each block can be mapped into mem-

ory or I/O space. Memory mapped regions can request

to be located below 1 MByte (Real Mode address

space for a PC). Each region also has a configurable

bus width for the Add-On bus interface. An 8-, 16-, or

32-bit Add-On interface may be selected, for use with

a variety of Add-On memory or peripheral devices.

Pass-Thru features can be used only when the S5335

is a PCI target. As a target, the S5335 Pass-Thru

mode supports single data transfers as well as burst

transfers. When accessed with burst transfers, the

S5335 supports data transfers at the full PCI band-

width. The data transfer rate is only limited by the PCI

initiator performing the access and the speed of the

Add-On logic.

FUNCTIONAL DESCRIPTION

To provide the PCI bus Add-On with direct access to

Add-On resources, the S5335 has an internal Pass-

Thru Address Register (APTA), and a Pass-Thru Data

both the PCI bus interface and the Add-On bus inter-

face. This allows a PCI initiator to perform Pass-Thru

writes (data transferred from the PCI bus to the Add-

On bus) or Pass-Thru reads (PCI bus requests data

from the Add-On bus). The S5335 Pass-Thru interface

supports both single cycle (one data phase) and burst

accesses (multiple data phases).

Pass-Thru Transfers

Data transfers between the PCI bus and the Add-On

using the Pass-Thru interface are implemented with a

handshaking scheme. If the PCI bus writes to an

S5335 Pass-Thru region, Add-On logic must read the

data from the S5335 and store it on the Add-On. If the

PCI bus reads from a Pass-Thru region, Add-On logic

must write data to the S5335.

Some applications may require that an address be

passed to the Add-On for Pass-Thru accesses. For

example, a 4 Kbyte Pass-Thru region on the PCI bus

may correspond to a 4 Kbyte block of SRAM on the

Add-On card. If a PCI initiator accessed this region,

the Add-On would need to know the offset within the

memory device to access. The Pass-Thru Address

information for the current PCI cycle. When the PCI

bus performs burst accesses, the APTA register is

updated by the S5335 to reflect the address of the cur-

rent data phase.

For PCI writes to the Add-On, the S5335 transfers the

data from the PCI bus into the Pass-Thru Data Regis-

ter (APTD). The S5335 captures the data from the PCI

bus when TRDY# is asserted. The PCI bus then

becomes available for other transfers. When the Pass-

Thru data register becomes full, the S5335 asserts the

Pass-Thru status signals to indicate to the Add-On that

data is present. The Add-On logic may read the data

access is complete. Until the current access com-

pletes, the S5335 responds to further Pass-Thru

accesses with retries.

For PCI reads from the Add-On, the S5335 asserts the

Pass-Thru status signals to indicate to the Add-On that

data is required. The Add-On logic should write to the

Pass-Thru Data Register and assert PTRDY# to com-

plete the access. The S5335 does not assert TRDY#

to the PCI bus until PTRDY# is asserted by Add-On

logic. If the Add-On cannot provide data quickly

enough, the S5335 signals a retry to the PCI bus. This

allows the PCI bus to perform other tasks, rather than

waiting for a slow target.

S5335 Datasheet(PDF) 140 Page - Applied Micro Circuits Corporation

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