AM79C901AVCT datasheet(37/90 Pages) AMD

37 / 90 page

Am79C901A

PR ELI M IN AR Y

Header AID Remote Control Word Commands

Stations may be configured either as master stations

or as slave stations. Only one master may exist on a

given HomePNA segment or network over which the

HomePNA PHY header is preserved.

The master station may send commands embedded in

the HomePNA header control word to remotely set var-

ious parameters of the remote slave stations. Stations

are identified via the AID as follows:

1. The master station is identified on the HomePNA

wire network with an AID of FFh.

2. A slave is identified with an AID of 00h to EFh.

3. AID values of F0h to FEh are reserved for future use.

Once a command has been transmitted, the master

station will revert to a slave AID, so that subsequent

control words are not interpreted by the slave stations

as new commands.

Master mode is entered by writing to the PHY control

completion of the command sequence.

A valid master remote command consists of three

HomePNA frames with an AID of FFh. Since the

HomePNA PHY header is prepended to packets re-

ceived from the MAC, as well as any1Home packets,

packets from the master station may be separated by

intervals during which other (slave) stations may

transmit their frames.

A remote master Control Word command will be recog-

nized and executed by a HomePNA PHY when it re-

ceives three consecutive valid HomePNA frames with

an AID of FFh.

Valid commands are as follows:

1. SET_POWER: Commands slave stations to set

their transmit level to a prescribed level until another

master command is received.

2. SET_SPEED: Commands slave stations to set their

transmit speed to a prescribed value until another

master command is received.

The control word bit encoding and possible values are

described in Table 9.

Table 9.

Master Station Control Word Functions

Slave stations transmit the following status messages

in the HomePNA header control word of all outgoing

frames:

1. VERSION_STATUS: The HomePNA PHY version of

the slave station. The receiving station must revert to

this version to interpret the packet.

2. POWER_STATUS: The transmit power level of the

transmitting slave station for the current frame. All

HomePNA units support both LOW_POWER and

HIGH_POWER modes of operation.

3. SPEED_STATUS: The transmit speed of the slave

station for the current frame. Receiving stations will

adjust their receiver parameters to correctly interpret

this frame.

The slave control word bit encoding is identical to the

master control word format.

1 Mbps HomePNA PHY Loopback

The HomePNA PHY is capable of supporting internal

loopback only.

Internal Loopback

In internal loopback, the transmitted data is returned to

the receive data bus without transmitting data on the

network. The MAC must be programmed to support

full-duplex operation and is responsible for comparing

the transmitted data to that received. Internal loopback

is accomplished by setting the “enable loopback mode”

in HPR0, bit 14, to 1.

any1Home Link Detection

While consuming minimal network resources, AMD’s

innovative any1Home Link Detection Packet provides a

means to indicate to the MAC, and thus the upper lay-

ers of the system protocol, that a valid network (as de-

fined by HomePNA) has been detected. The Link

Detection Packet is also capable of detecting a network

failure and allows the upper layer protocol to take cor-

rective action. Thus, the any1Home Packet provides

link indication that the MAC requires for compliance to

the Microsoft PC98, PC99, and HomePNA revision 1.1

requirements without utilizing resources from the upper

layers of the system protocol

AID

Bit No.

Command Function

LSB

0 = version 0

5MSB

0 = Set to low-power transmit mode.

1 = Set to high-power transmit mode.

6LSB

0 = Set to low-speed transmit mode.

1 = Set to high-speed transmit mode.

6MSB

Reserved

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