DP83266VF National Semiconductor, DP83266VF Datasheet - Page 85

• Manufacturer Part Number: DP83266VF
• Description: IC MEDIA ACSS CTRL INTF 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83266VF

• Applications: *
• Voltage - Supply: 4.75 V ~ 5.25 V
• Package / Case: 160-BFQFP
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Other names: *DP83266VF

7 0 Control Information
(Continued)
Late Count Counter (LTCT)
The Late Count Counter (LTCT) is implemented differently than suggested by the FDDI MAC Standard but provides similar
information The function of the Late Count Counter is divided between the Late Flag and a separate counter The Late Flag
is equivalent to the Standard Late Count with a non-zero value It is maintained by the Ring Engine to indicate if it is possible to
send asynchronous traffic When the ring is operational Late Count indicates the time it took the ring to recover the last time the
ring went non-operational When the ring is non-operational Late Count indicates the time it has taken (so far) to recover the
ring
The Late Count is provided to assist Station Management in the isolation of serious ring errors In many situations it is helpful for
SMT to know how long it has been since the ring went non-operational in order to determine if it is necessary to invoke recovery
procedures When the ring becomes non-operational there is no way to know how long it will stay non-operational therefore a
timer is necessary If the Late Count Counter is not provided SMT would be forced to start a timer every time the ring goes non-
operational even though it may seldom be used By using the provided Late Count Counter an SMT implementation may be able
to alleviate this additional overhead
The Late Count Counter is incremented every time TRT expires while the ring is non-operational and Late Flag is set (once
every TMAX) This counter is never writable not even in Stop Mode The counter is set to Zero as a result of a MAC Reset when
a Beacon or Claim Request is not also present (Function MCRST is set and Function BCN and Function CLM are not set) and
every time the ring becomes non-operational Late Count Counter is a sticky counter at 15
Events reported in the Token and Timer Event Latch Register (TELR0 CBERR TELR0 TRTEXP) can be used to determine that
Late Count Counter has incremented No overflow event is provided
Access Rules
Address
Read
Write
09Fh
Always
N A
Register Bits
D7
D6
D5
D4
D3
D2
D1
D0
LTCT
Zero
Zero
Zero
Zero
CT3
CT2
CT1
CT0
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