DP83251V datasheet(39/96 Pages) NSC

39 / 96 page

50 Registers (Continued)

NOISE PRESCALE THRESHOLD REGISTER (NPTR)

The Noise Prescale Threshold Register contains the start value for the Noise Prescale Counter The Noise Prescale Counter is a

count-down counter and it is used in conjunction with the Noise Counter for counting the Noise events The Noise Prescale

Counter decrements once every 80 ns while there is a noise event When the Noise Prescale Counter reaches zero it reloads

the count with the content of the Noise Prescale Threshold Register and also causes the Noise Counter to decrement

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

the following conditions is true

(1) Both the Noise Counter and Noise Prescale Counter reach zero and the current Line State is either Noise Line State Active

Line State or Line State Unknown

(2) The current Line State is either Halt Line State Idle Line State Master Line State Quiet Line State or No Signal Detect

(3) The Noise Threshold Register or Noise Prescale Threshold Register goes through a Control Bus Interface write cycle

In addition the value of the Noise Prescale Threshold register is loaded into the Noise Prescale Counter if the Noise Prescale

Counter reaches zero

The Noise Counter and Noise Prescale Counter will continue to count without resetting or reloading the threshold values if a

Line State change occurs and the new line state is either Noise Line State Active Line State or Line State Unknown

When both the Noise Threshold Counter and Noise Counter both reach zero the Noise Threshold bit of the Receive Condition

ACCESS RULES

ADDRESS

READ

WRITE

0Eh

Always

NPT7

NPT6

NPT5

NPT4

NPT3

NPT2

NPT1

NPT0

Bit

Symbol

Description

NPT0

NOISE PRESCALE THRESHOLD BIT k0l

Least significant bit (LSB) of the

start value of the Noise Prescale Counter

D1–6

NPT1–6

NOISE PRESCALE THRESHOLD BITk1–6l

Intermediate bits of start

value for the Noise Prescale Counter

NPT7

NOISE PRESCALE THRESHOLD BIT k7l

Most significant bit (MSB) of the

start value for the Noise Prescale Counter

DP83251V Datasheet(PDF) 39 Page - National Semiconductor (TI)

DP83251V Datasheet(HTML) 39 Page - National Semiconductor (TI)

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