AM79C976 datasheet(114/309 Pages) AMD

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114

Am79C976

8/01/00

P R E L I M INARY

cleared by writing a 1. Writing a 0

has

effect.

RTABORT

cleared by H_RESET and is not

affected by S_RESET or by set-

ting the STOP bit.

STABORT

Send Target Abort. Read as ze-

ro; write operations have no ef-

fect. The Am79C976 controller

will never terminate a slave ac-

cess with a target abort se-

quence.

STABORT is read only.

10-9

DEVSEL

Device Select Timing. DEVSEL

is set to 01b (medium), which

means that the Am79C976 con-

troller will assert DEVSEL two

clock periods after FRAME is as-

serted.

DEVSEL is read only.

DATAPERR Data

Parity

Error

Detected.

DATAPERR is set when the

Am79C976 controller is the cur-

rent bus master and it detects a

data parity error and the Parity

Error Response enable bit (PCI

Command register, bit 6) is set.

During the data phase of all

memory read commands, the

Am79C976 controller checks for

parity error by sampling the

AD[31:0] and C/BE[3:0] and the

PAR lines. During the data phase

of all memory write commands,

the Am79C976 controller checks

the PERR input to detect whether

the target has reported a parity

error.

DATAPERR

set

the

Am79C976

controller

and

cleared by writing a 1. Writing a 0

has no effect. DATAPERR is

cleared by H_RESET and is not

affected by S_RESET or by set-

ting the STOP bit.

FBTBC

Fast

Back-To-Back

Capable.

Read as one; write operations

have no effect. The Am79C976

controller is capable of accepting

fast

back-to-back

transactions

with the first transaction address-

ing a different target.

6-5

RES

Reserved locations. Read as

zero; write operations have no ef-

fect.

NEW_CAP New Capabilities. This bit indi-

cates whether this function imple-

ments

list

extended

capabilities such as PCI power

management. When set, this bit

indicates the presence of New

Capabilities. A value of 0 means

that this function does not imple-

ment New Capabilities.

Read as one; write operations

have no effect. The Am79C976

controller supports the Linked

Additional Capabilities List.

3-0

RES

Reserved locations. Read as

zero; write operations have no ef-

fect.

3&,5HYLVLRQ,' 5HJLVWHU

Offset 08h

The PCI Revision ID register is an 8-bit register that

specifies the Am79C976 controller revision number.

The value of this register is 5Xh with the lower four bits

being silicon-revision dependent.

The PCI Revision ID register is read only.

3&,3URJUDPPLQJ ,QWHUIDFH 5HJLVWHU

Offset 09h

The PCI Programming Interface register is an 8-bit reg-

ister that identifies the programming interface of

Am79C976 controller. PCI does not define any specific

es. The value of this register is 00h.

The PCI Programming Interface register is read only.

3&,6XE&ODVV5HJLVWHU

Offset 0Ah

The PCI Sub-Class register is an 8-bit register that iden-

tifies specifically the function of the Am79C976 control-

ler. The value of this register is 00h which identifies the

Am79C976 device as an Ethernet controller.

The PCI Sub-Class register is read only.

3&,%DVH&ODVV5HJLVWHU

Offset 0Bh

The PCI Base-Class register is an 8-bit register that

broadly classifies the function of the Am79C976 con-

troller. The value of this register is 02h which classifies

the Am79C976 device as a network controller.

The PCI Base-Class register is read only.

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