AM79C983A datasheet(18/60 Pages) AMD

18 / 60 page

Am79C983A

PRELIMINARY

a. Standard reconnection algorithm—A data packet

longer than 512-bit times (nominal) is transmitted or re-

ceived by the partitioned port without a collision.

b. Alternate reconnection algorithm—A data packet

longer than 512-bit times (nominal) is transmitted by

the partitioned port without a collision.

Basic Management Functions

Repeater Management

The IMR2 management functions are a super-set of

the those provided by the AMD’s IMR+/HIMIB device

chipset. The IMR2 device contains the complete set of

repeater and port functions as deﬁned in ANSI/IEEE

802.3,

Repeater Management Standard, (Section 19).

All mandatory and optional capabilities are supported.

These include the Basic Control, Performance Monitor-

ing, and Address Tracking packages. Additionally,

Node Address Mapping, MAU Management speciﬁc

functions, and intrusion protection functions are in-

cluded. Support is also provided for the RMON MIB

RFC 1757.

All information is stored in registers which can be ac-

cessed through the Microprocessor Interface (Node

Processor Port). The register location is deﬁned by a

Address and data of the registers are multiplexed using

the C/D pin. The register address is selected by writing

to the Node Processor Port with C/D HIGH. The regis-

ter data is selected by writing or reading to the Node

Processor Port with C/D LOW.

Many of the registers are larger than 1 byte. For these

registers, consecutive accesses to register data (equal

to the number of bytes in the register) are required. The

order is LSByte to MSByte. For a write operation, if the

address changes before all the bytes are written, the

The Status Register is accessed by reading the Node

Processor Port with the C/D pin HIGH. This reduces

the number of operations necessary to access the

Status Register.

All bit ﬁelds are ordered such that the left most bit is the

most signiﬁcant bit. Unused register banks, ports and

cessed as this may cause device malfunction. When

specifying the register bank or port number, the follow-

ing format is used:

P4:0 represent the Register Bank or Port Number, or-

ganized as follows:

P = P4 P3 P2 P1 P0

Port/Register Bank

Repeater Registers

Interrupt Registers

Interrupt Control Registers

Port Control Registers

Port Status Registers

RMON Registers

Packet Report Registers

16- 30

Port Attributes

The register to be accessed for reading or writing is

speciﬁed by writing the following control byte to the

C register:

R = R4 R3 R2 R1 R0

Figure 1 shows the Management Register Map, and

Table 1 shows register banks and register assignments

within the register banks.

RMON

Remote monitoring (RMON) functions are designed to

give the management system the capability to remotely

monitor the hub for diagnostic purposes. The rules for

RMON are described in the RMON MIB (as of this

writing IETF RFC1578).

The IMR2 device provides direct support for both the

statistics and history object groups. Indirect support is

provided for the alarm, host, hostTopN, event, and ma-

trix groups. Direct support is provided via the RMON

support is provided through the Packet Report Port.

Packet Reports

The IMR2 device generates status information on

every packet that it repeats. The data is transmitted

over the Packet Report Port. The data format consists

of the beginning of the packet followed by a packet tag

and statistical data on the packet.

C Port Write

MSB

LSB

C Port Write

MSB

LSB

Preamble DA SA T/L Packet Data

Var. Length

Tag &

FCS

Port No., New

Status

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