DP83266 datasheet(83/152 Pages) NSC

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70 Control Information (Continued)

Negotiated Target Rotation Time (TNEG0 – 3)

The Negotiated Target Rotation Time (TNEG0 – 3) is a 32-bit twos complement value It is the result of the Claim process TNEG

is loaded either directly from the received Claim Information field (T

Bid

Rc) or via the Control Interface

The first byte of TNEG (bits TNEG(31 – 24)) always contains FFh TNEG has a maximum value of 134 seconds and a resolution

of 80 ns

TRT is loaded with TNEG when the Ring

Operational flag is set TNEG is not automatically compared with TREQ when the

Ring

Operational flag is set This should be checked by software whenever the ring becomes operational to make sure that

TNEG is less than or equal to TREQ

An implementation of the SM

ControlRequest (Reset) should load TNEG with TMAX to remove any possibility of the station

entering Claim early

On a Master Reset (bit MARST in the Function Register is set) TNEG is set to FFE00000 which corresponds to 167772 ms

the default TMAX specified by the FDDI MAC Standard

Access Rules

Address

Read

Write

098–09Bh

Always

Stop Mode

TNEG0

TNEG(31)

TNEG(30)

TNEG(29)

TNEG(28)

TNEG(27)

TNEG(26)

TNEG(25)

TNEG(24)

TNEG1

TNEG(23)

TNEG(22)

TNEG(21)

TNEG(20)

TNEG(19)

TNEG(18)

TNEG(17)

TNEG(16)

TNEG2

TNEG(15)

TNEG(14)

TNEG(13)

TNEG(12)

TNEG(11)

TNEG(10)

TNEG(9)

TNEG(8)

TNEG3

TNEG(7)

TNEG(6)

TNEG(5)

TNEG(4)

TNEG(3)

TNEG(2)

TNEG(1)

TNEG(0)

DP83266 Datasheet(PDF) 83 Page - National Semiconductor (TI)

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