PCI9060ES datasheet(29/192 Pages) ETC

29 / 192 page

SECTION 3

PCI 9080

FUNCTIONAL DESCRIPTION

©PLX Technology, Inc., 1997

Page 20

Version 1.02

PCI 9080 never prefetches beyond the region specified

for direct master accesses.

3.6.1.4 IO/CFG Access

When a Local Direct Master I/O access to the PCI bus is

made,

the

PCI

Configuration

Address

Configuration Enable bit determines if an I/O or

configuration access is to be made to the PCI bus.

Local burst accesses are broken into single PCI I/O

address/data cycles. PCI 9080 does not prefetch read

data for I/O and CFG reads.

For Direct Master I/O or Configuration cycles, PCI 9080

asserts the same PCI bus byte enables as asserted on

the local bus.

3.6.1.5 I/O

If the Configuration Enable bit is clear, a single I/O

access is made to the PCI bus. The local address,

remapped decode address bits and the local byte

enables are encoded to provide the address and is

output with an I/O read or write command during the PCI

address cycle.

For writes, data is loaded into the write FIFO and

READYo# returned to the Local bus. For reads, PCI

9080 holds off READYo# while gathering an Lword from

the PCI bus.

When the I/O remap select bit is set to a value of 1,

these PCI address bits [31:16] are forced to a value of 0

(refer to Table 4-43[13]).

3.6.1.6 CFG (PCI Configuration Type 0 or

Type 1 Cycles)

If the Configuration Enable bit is set, a CFG access is

made to the PCI bus. In addition to enabling the

configuration (bit 31) of (PCI:2Ch)(LOC:ACh) (refer to

Table 4-44[31]), the user must provide all register

information. The register number (bits [7:2]) or the

device number (bits [15:11]) must be modified and a new

CFT read/write cycle must be performed before other

registers or devices can be accessed.

If the PCI Configuration Address Register selects a Type

0 command, bits [10:0] from the register are copied to

address bits [10:0]. Bits [15:11] (“device number”) are

translated into a single bit being set in PCI address bits

[31:11]. PCI address bits [31:11] can be used as a

device select. For a Type 1 command, bits [23:0] are

copied from the register to bits [23:0] of the PCI address.

PCI address bits [31:24] are 0. A configuration read or

write command code is output with the address during

the PCI address cycle (refer to Table 4-44).

For writes, local data is loaded into the write FIFO and

READYo# is returned. For reads, PCI 9080 holds off

READYo# while gathering an Lword from the PCI bus.

Example 1—To perform a Type 0 configuration cycle to

PCI device on AD[21].

PCI 9080 must be configured to allow Direct Master

access to the PCI buses. PCI 9080 must also be set

to respond to I/O space accesses. These bits must

be set in (LOC:04h):

•

Field 0 = I/O Space = 1

•

Field 2 = Master Enable = 1

Direct Master Range is selected by the board

designer. For this example, use a range of 1 MB:

•

1 MB = 2

20 = 000FFFFFh

Value to program into the range register is the

inverse of 000FFFFFh, which is FFF00000h:

•

(LOC:9Ch) = FFF00000h

Local Base Address for Direct Master to PCI IO/CFG

is determined by the board designer. For this

example, use 40000000h:

•

(LOC:A4h) = 40000000h

PCI Address (Remap) for Direct Master to PCI

Memory Register must enable Direct Master I/O

access. This bit must be set in (LOC:A8h):

•

Field 1 = Direct Master I/O Access Enable = 1

PCI

must

know

which

PCI

device

and

PCI

configuration register the PCI configuration cycle is

accessing. For this example, access the PCI device

on AD[21]. Also access the PCI Base Address 0 for

Memory Mapped Configuration Register (PCI:10h).

(PCI:10h) is the fourth register, counting from 0 (use

Table

4-5,

“PCI

Configuration

Registers,”

for

reference). These bits must be set in (LOC:ACh):

•

Fields 1:0 = Configuration Type 0 = 00b

•

Fields 7:2 = Register number = The fourth

this field, beginning with bit 2 = 000100b

•

Fields 10:8 = Function Number = 000b

•

Fields 15:11 = Device Number = n-11, where

n is the value in AD[n]=21-11 = 10 = 01010b

•

Fields 23:16 = Bus Number = 00000000b

•

Field 31 = Configuration Enable = 1

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