AM79C873 datasheet(10/44 Pages) AMD

10 / 44 page

Am79C873

PRELIMINARY

LNKSTS

Link Status Register Bit

Output

This pin reﬂects the status of bit 2 register 1.

OPMODE0-OPMODE3

Input

These pins are used to control the forced or advertised

operating mode of the NetPHY-1 device (see table be-

low). The value is latched into the NetPHY-1 device reg-

isters at power-up/rese..

RTPR/NODE

Repeater/Node Mode

Input

When set high, this bit selects REPEATER mode; when

set low, it selects NODE. In REPEATER mode or

NODE mode with Full Duplex conﬁgured, the Carrier

Sense (CRS) output from the NetPHY-1 device will be

asserted only during receive activity. In NODE mode or

a mode not conﬁgured for Full Duplex operation, CRS

will be asserted during receive or transmit activity. At

power-up/reset, the value on this pin is latched into

BPALIGN

Bypass Alignment

Input

This pin allows 100 Mbps transmit and receive data

streams to bypass all of the transmit and receive oper-

ations when set high. At power-up/reset, the value on

this pin is latched into bit Register 16, bit 13.

BP4B5B

Bypass 4B5B Encoder/Decoder

Input

This pin allows 100 Mbps transmit and receive data

streams to bypass the 4B to 5B encoder and 5B to 4B

decoder circuits when set high. At power-up/reset, the

value on this pin is latched into Register 16, bit 15.

BPSCR

Bypass Scrambler/Descrambler

Input

This pin allows 100 Mbps transmit and receive data

streams to bypass the scrambler and descrambler cir-

cuits when set high. At power-up/reset, the value on

this pin is latched into Register 16, bit 14.

10BTSER

Serial/Nibble Select

Input

10 Mbps Serial Operation:

When set high, this input selects a serial data transfer

mode. Manchester encoded transmit and receive data

is exchanged serially with a 10 MHz clock rate on the

least signiﬁcant bits of the nibble-wide MII data buses,

pin TXD[0] and RXD[0] respectively. This mode is in-

tended for use with the NetPHY-1 device connected to

a device (MAC or Repeater) that has a 10 Mbps serial

interface. Serial operation is not supported in 100 Mbps

mode. For 100 Mbps, this input is ignored.

10 and 100 Mbps Nibble Operation:

When set low, this input selects the MII compliant nib-

ble data transfer mode. Transmit and receive data is ex-

changed in nibbles on the TXD[3:0] and RXD[3:0] pins

respectively.

At power-up/reset, the value on this pin is latched into

OP-

MODE3

OP-

MODE2

OP-

MODE1

OP-

MODE0

Function

000

Auto-Negotiation

enable with all

capabilities with

Flow Control

001

Auto-Negotiation

enable without all

capabilities without

Flow Control

010

Auto-Negotiation

100TX FDX with

Flow Control only

011

Auto-Negotiation

100TX FDX/HDX

without Flow

Control

100

Auto-Negotiation

10TP FDX with

Flow Control only

101

Auto-Negotiation

10TX FDX/HDX

without Flow

Control

110

Manual select

100TX FDX

111

Manual select

100TX HDX

000

Manual select

10TX FDX

001

Manual select

10TX HDX

010

Manual select

100FX FDX

011

Manual select

100FX HDX

111

Auto-Negotiation

10/100TX. HDX

only

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