AM79C976 datasheet(207/309 Pages) AMD

207 / 309 page

8/01/00

Am79C976

207

P R E L I M INARY

affected by S_RESET or setting

the STOP bit.

RES

Reserved location. Written and

read as zeros.

RCVE

Receive Status Enable. When

this bit is set, a value of 1 is

passed to the LEDOUT bit in this

tivity on the network.

Read/Write accessible. RCVE is

cleared by H_RESET and is not

affected by S_RESET or setting

the STOP bit.

SFBDE

Start Frame/Byte Delimiter En-

able. When this bit is set, a value

of 1 is passed to the LEDOUT bit

in this register when the RXD[3:0]

pins are presenting the least sig-

nificant nibble of valid frame data.

Read/Write accessible. RCVE is

cleared by H_RESET and is not

affected by S_RESET or setting

the STOP bit.

COLE

Collision Status Enable. When

this bit is set, a value of 1 is

passed to the LEDOUT bit in this

activity on the network.

Read/Write accessible. COLE is

set to 1 by H_RESET and is not

affected by S_RESET or setting

the STOP bit.

%&5)XOO'XSOH[ &RQWURO

Note: Bits 15-0 in this register are programmable

through the EEPROM.

Bit

Name

Description

31-16

RES

Reserved locations. Written as

zeros and read as undefined.

15-3

RES

Reserved locations. Written as

zeros and read as undefined.

FDRPAD

Full-Duplex Runt Packet Accept

Disable. When FDRPAD is set to

1 and full-duplex mode is en-

abled, the Am79C976 controller

will only receive frames that meet

the

minimum

Ethernet

frame

length of 64 bytes. Receive DMA

will not start until at least 64 bytes

or a complete frame have been

received.

When

FDRPAD

cleared to 0, the Am79C976 con-

troller will accept any frame of 12

bytes or greater, and receive

DMA will start according to the

programming of the receive FIFO

watermark.

Read/Write accessible. FDRPAD

is set to 1 by H_RESET and is not

affected by S_RESET or by set-

ting the STOP bit.

RES

Reserved locations. Written as

zeros and read as undefined.

FDEN

Full-Duplex Enable. FDEN con-

trols whether full-duplex opera-

tion is enabled. When FDEN is

cleared and the Auto-Negotiation

is disabled, full-duplex operation

not

enabled

and

the

Am79C976 controller will always

operate in the half-duplex mode.

When

FDEN

set,

the

Am79C976 controller will operate

in full-duplex mode when the MII

port is enabled. Do not set this

bit when Auto-Negotiation is

enabled.

Read/Write accessible. FDEN is

reset to 0 by H_RESET, and is

unaffected by S_RESET and the

STOP bit.

%&5,2 %DVH $GGUHVV /RZHU

Bit

Name

Description

31-16

RES

Reserved locations. Written as

zeros and read as undefined.

15-5

IOBASEL

Reserved

locations.

After

H_RESET, the value of these bits

will be undefined. The settings of

these bits will have no effect on

any Am79C976 controller func-

tion. It is only included for soft-

ware

compatibility

with

other

PCnet family devices.

Read/Write

accessible.

IO-

BASEL

not

affected

S_RESET or STOP.

4-0

RES

Reserved locations. Written as

zeros, read as undefined.

AM79C976 Datasheet(PDF) 207 Page - Advanced Micro Devices

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