DP83256VF datasheet(62/144 Pages) NSC

62 / 144 page

50 Registers (Continued)

518 STATE THRESHOLD REGISTER (STR)

The State Threshold Register contains the start value for the State Timer This timer is used in conjunction with the State

Prescale Timer to count the Line State duration The State Timer will decrement every 80 ns if the State Prescale Timer is zero

and the current Line State is Halt Line State Idle Line State Master Line State Quiet Line State or No Signal Detect The State

Timer takes

((SPTRa1) x STR a SPTR) x 80 ns

to reach zero during a continuous line state condition

The threshold values for the State Timer and State Prescale Timer are simultaneously loaded into both counters if one of the

following conditions is true

1 Both the State Timer and State Prescale Timer reach zero and the current Line State is Halt Line State Idle Line State

Master Line State Quiet Line State or No Signal Detect

2 A line state change occurs and the new Line State is Halt Line State Idle Line State Master Line State Quiet Line State or

No Signal Detect

3 The State Threshold Register or State Prescale Threshold Register goes through a Control Bus Interface write cycle

In addition the value of the State Prescale Threshold Register is loaded into the State Prescale Counter if the State Prescale

Timer reaches zero

The State Timer and State Prescale Timer will reset by reloading the threshold values if a Line State change occurs and the

new Line State is Halt Line State Idle Line State Master Line State Quiet Line State or No Signal Detect On detection of ALS

NLS or LSU the timer will not decrement

ACCESS RULES

ADDRESS

READ

WRITE

11h

Always

RES

ST6

ST5

ST4

ST3

ST2

ST1

ST0

Bit

Symbol

Description

D0-D6

ST0-ST6

STATE THRESHOLD BITk0-6l

Start value for the State Timer

ST0 is the Least Significant Bit (LSB)

RES

RESERVED

Reserved for future use

Note

Users are discouraged from using this bit Write data is ignored since the reserved bit is permanently set to 0

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