DP83266 datasheet(76/152 Pages) NSC

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70 Control Information (Continued)

752 Group Addresses

The Ring Engine supports detection of Group Addresses within programmable and fixed blocks of consecutive addresses The

algorithm used by the Ring Engine first performs a comparison between the most significant bits of the received DA with

programmable and fixed addresses If the most significant bits match the remaining bits are used as an index into a programma-

ble bit map If the indexed bit is 1 the A

Flag is set to 1 if the indexed bit is 0 the A

Flag remains 0

One programmable block of 256 group addresses is supported for group long addresses (GLA) and one programmable block of

group addresses is supported for group short addresses (GSA) Both of the programmable ranges share the same programma-

ble group address map (PGM)

For short addresses the first byte of a received DA is compared with GSA0 (bits GSA(15 – 8)) If they match then the second

byte is used as an index into the PGM For long addresses the first 5 bytes of a received DA are compared with GLA0 through

GLA4 (bits GLA(47 – 8)) If all 5 of these bytes match the corresponding byte in the received DA then the 6th byte of the

received DA is used as an index into the PGM The last byte of the address is used as an index into the PGM in both long and

short group addressing

A fixed block of 16 group addresses is supported for both long and short addresses at the end of the address space that

includes the UniversalBroadcast address (FF

FF) For short addresses if the first 12 bits of the received DA are all 1’s then

the last 4 bits are used as an index into the 16-bit Fixed Group Map (FGM) Similarly for long addresses if the first 44 bits are all

1’s the last 4 bits are also used as an index into the 16-bit FGM

The Group Addresses should be valid for at least 12 byte times before the Addressing Mode is enabled and should remain valid

for at least 12 byte times after the Addressing Mode is disabled in order to guarantee proper detection

Bits ELA (Enable Long Addressing) and ESA (Enable Short Addressing) in the Option Register determine the address types that

will be recognized by this MAC

Alternative group addressing schemes may be implemented using external matching logic that monitors the byte stream at the

PHY Interface The result of the comparison is returned using the EA (External A

Flag) input signal

Group Long Address (GLA0 – GLA4)

Group Long Address (GLA0 – GLA4) represents the first 5 bytes of the long address bit GLA(47) to bit GLA(8)

To disable Long Group Address matches bits GLA(46 – 8) should be set to all One’s

Access Rules

Address

Read

Write

048–04Ch

Stop Mode

GLA0

GLA(47)

GLA(46)

GLA(45)

GLA(44)

GLA(43)

GLA(42)

GLA(41)

GLA(40)

GLA1

GLA(39)

GLA(38)

GLA(37)

GLA(36)

GLA(35)

GLA(34)

GLA(33)

GLA(32)

GLA2

GLA(31)

GLA(30)

GLA(29)

GLA(28)

GLA(27)

GLA(26)

GLA(25)

GLA(24)

GLA3

GLA(23)

GLA(22)

GLA(21)

GLA(20)

GLA(19)

GLA(18)

GLA(17)

GLA(16)

GLA4

GLA(15)

GLA(14)

GLA(13)

GLA(12)

GLA(11)

GLA(10)

GLA(9)

GLA(8)

Note

GLA(47) should always be set to One

Group Short Address (GSA0)

Group Short Address (GSA0) represents the station’s short 16-bit address bit GSA(15) to bit GSA(8)

It is possible to disable Short Group Addressing by programming bits GSA(14 – 8) to all Ones

Access Rules

Address

Read

Write

04Eh

Stop Mode

GSA0

GSA(15)

GSA(14)

GSA(13)

GSA(12)

GSA(11)

GSA(10)

GSA(9)

GSA(8)

Note

GSA(15) is not used in the comparison since the comparison will only be accomplished if the received DA(15) is a One

DP83266 Datasheet(PDF) 76 Page - National Semiconductor (TI)

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