DP83266 datasheet(89/152 Pages) NSC

89 / 152 page

70 Control Information (Continued)

Token Received Counter (TKCT)

The Token Received Counter (TKCT) maintains the count of valid tokens received by this station The counter can be used with

the Ring Latency Counter to calculate the average network load over a period of time The frequency of token arrival is inversely

related to the network load

The Token Received Counter is incremented every time a valid token arrives

Interrupts are available on increment (CILRTKRCVD) and when the 20-bit counter overflows and wraps around

(COLRTKRCVD)

Access Rules

Address

Read

Write

0B8–0BBh

Always

Stop Mode

TKCT0

Zero

TKCT1

Zero

CT19

CT18

CT17

CT16

TKCT2

CT15

CT14

CT13

CT12

CT11

CT10

CT9

CT8

TKCT3

CT7

CT6

CT5

CT4

CT3

CT2

CT1

CT0

Ring Latency Counter (RLCT)

The Ring Latency Counter (RLCT) is a measurement of time for PDUs to propagate around the ring This counter contains the

last measured ring latency whenever the RLVD bit of the Token and Timer Event Latch Register (TELR0RLVD) is One

The current ring latency is measured by timing the propagation of a My

Void frame around the ring A new latency measure-

ment can be requested by clearing the Ring Latency Valid bit of the Token Event Register (TELR0RLVLD)

When the ring is operational the next early token is captured Before the token is re-issued a My

Void frame is transmitted and

the Ring Latency Counter (RLCT) is reset The token will not be captured if the Inhibit Token Capture Option (OptionITC) is set

and the ring latency will not be measured

When the ring is not operational ring latency timing will commence at the end of the next immediate request A My

Void is

transmitted and RLCT is reset This could be used to time how long the ring is non-operational since the My

Void frame will not

return

The Ring Latency Counter increments once every 16 byte times from when the Ending Delimiter of the My

Void frame is

transmitted until the Ending Delimiter of the My

Void frame returns When the My

Void frame returns the ring latency valid bit

(TELR0RLVLD) is set and may cause an interrupt When set RELRRLVLD indicates that RLCT will be valid to within 128 ms

The Ring Latency Counter can measure ring latencies up to 13421772 seconds with accuracy of 128 ms

The ring latency timing function is automatically disabled when exceptions are detected and retried at the next opportunity

Since a Master Reset (FunctionMARST) causes TELR0RLVLD to be cleared the ring latency will automatically be measured

on the first opportunity (at the end of the first immediate request or with the first early token) Note that if a duplicate of this MAC

address exists on the ring the My

Void frame will be stripped and the ring latency measurement will never complete

Access Rules

Address

Read

Write

0BC–0BFh

Always

Stop Mode

RLCT0

Zero

RLCT1

Zero

CT19

CT18

CT17

CT16

RLCT2

CT15

CT14

CT13

CT12

CT11

CT10

CT9

CT8

RLCT3

CT7

CT6

CT5

CT4

CT3

CT2

CT1

CT0

DP83266 Datasheet(PDF) 89 Page - National Semiconductor (TI)

DP83266 Datasheet(HTML) 89 Page - National Semiconductor (TI)

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