DP83261AVF datasheet(53/132 Pages) NSC

53 / 132 page

60 Control Information (Continued)

Group Short Address

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

4Eh

Stop Mode

GSA4

GSA(15)

GSA(14)

GSA(13)

GSA(12)

GSA(11)

GSA(10)

GSA(9)

GSA(8)

Design Note

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

Fixed Group Address MAP (FGM0 – FGM1)

If the first 44 bits of a long DA DA(47 – 4) or if the first 12 bits of a short DA DA(15 – 4) are 1 the last 4 bits of the DA DA(3 – 0)

are used as an index into FGM

The 4-bit index into FGM can be viewed in two different ways It can be viewed as 4 bits selecting one of 16 bits where the

hexidecimal equivalent of DA(3 – 0) can be used as the index For example the broadcast address would index FGM(F) Alterna-

tively it can be viewed as one bit DA(3) selecting the byte (FGM0 or FGM1) and three bits DA(2 – 0) selecting one of 8 bits

within a byte

ACCESS RULES

Address

Read

Write

58 – 59h

Stop Mode

FGM0

FGM(7)

FGM(6)

FGM(5)

FGM(4)

FGM(3)

FGM(2)

FGM(1)

FGM(0)

FGM1

FGM(F)

FGM(E)

FGM(D)

FGM(C)

FGM(B)

FGM(A)

FGM(9)

FGM(8)

Note

Bit FGM(F) must be set to One to ensure proper handling of frames with the UniversalBroadcast address including the SMT NSA frames This is mandatory

for interoperability on an FDDI Ring

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