dp83261 National Semiconductor Corporation, dp83261 Datasheet - Page 60

• Manufacturer Part Number: dp83261
• Description: Bmac Device Fddi Media Access Controller
• Manufacturer: National Semiconductor Corporation

6 0 Control Information
Negotiated Target Rotation Time (TNEG)
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 1 34 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 Control Request (Reset) should load TNEG with TMAX to remove any possibility of the station
entering Claim early
On a Master Reset (Function MARST is set) TNEG is set to FFE00000 which corresponds to 167 772 ms the default TMAX
specified by the FDDI MAC Standard
ACCESS RULES
TNEG0
TNEG1
TNEG2
TNEG3
Address
98 – 9Bh
TNEG(31)
TNEG(23)
TNEG(15)
TNEG(7)
D7
Always
Read
TNEG(30)
TNEG(22)
TNEG(14)
TNEG(6)
D6
(Continued)
Stop Mode
TNEG(29)
TNEG(21)
TNEG(13)
TNEG(5)
Write
D5
TNEG(28)
TNEG(20)
TNEG(12)
TNEG(4)
D4
60
TNEG(27)
TNEG(19)
TNEG(11)
TNEG(3)
D3
TNEG(26)
TNEG(18)
TNEG(10)
TNEG(2)
D2
TNEG(25)
TNEG(17)
TNEG(9)
TNEG(1)
D1
TNEG(24)
TNEG(16)
TNEG(8)
TNEG(0)
D0