AM79C873KCW datasheet(18/44 Pages) AMD

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Am79C873

PRELIMINARY

supports, a connection will be automatically estab-

lished using that technology. This allows devices that

do not support Auto-Negotiation but support a common

mode of operation to establish a link.

MII Serial Management

The MII serial management interface consists of a data

interface, basic register set, and a serial management

interface to the register set. Through this interface it is

possible to control and conﬁgure multiple PHY devices,

get status and error information, and determine the

type and capabilities of the attached PHY device(s).

The NetPHY-1 devices management functions corre-

spond to MII speciﬁcation for IEEE 802.3u-1995

(Clause 22) for registers 0 through 6 with vendor-spe-

ciﬁc registers 16,17, and 18.

In read/write operation, the management data frame is

64-bits long and starts with 32 contiguous logic one bits

(preamble) synchronization clock cycles on MDC. The

Start of Frame Delimiter (SFD) is indicated by a <01>

pattern followed by the operation code (OP):<10> indi-

cates Read operation and <01> indicates Write opera-

tion. For read operation, a 2-bit turnaround (TA) ﬁling

between Register Address ﬁeld and Data ﬁeld is pro-

vided for MDIO to avoid contention. Following the turn-

around time, 16-bit data is read from or written onto

management registers.

Serial Management Interface

The serial control interface uses a simple two-wired se-

rial interface to obtain and control the status of the phys-

ical layer through the MII interface. The serial control

interface consists of Management Data Clock (MDC),

and Management Data Input/Output (MDI/O) signals.

The MDIO pin is bidirectional and may be shared by up

to 32 devices.

Figure 5.

Management Interface - Read Frame Structure

Figure 6.

Management Interface - Write Frame Structure

32 "1"s

A4A3A0

Idle Preamble

SFD

Op Code

PHY Address

Turn Around

Data

Idle

Read

Write

MDC

MDIO Read

D15

D14

22164A-7

32 "1"s

Idle

Preamble

SFD

Op Code

PHY Address

Turn Around

Data

Idle

Write

MDC

MDIO Write

D15

D14

22164A-8

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