GS6151 datasheet(42/77 Pages) SEMTECH

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GS6151

Final Data Sheet

Rev.4

PDS-060389

August 2015

42 of 77

Semtech

Proprietary & Confidential

www.semtech.com

Figure 4-23: HEM Eye Width vs. Input Jitter

The eye scan state machine counts errors at each of the 128 phases to determine the

above eye parameters, returning a 1 in the appropriate bit of the bitmap for an error-free

measurement, and a 0 when an error has been detected. The length of each

measurement, SAMPLE_TIME, is determined by Equation 4-4 .

Equation 4-4

In Equation 4-4 , MEASUREMENT_PREDIVIDER and MEASUREMENT_TIME are bits of the

EYE_MON_CONTROL_REG_1 and EYE_MON_CONTROL_REG_2 registers, respectively.

By default MEASUREMENT_PREDIVIDER is set to 4x (bit value 0) and

MEASUREMENT_TIME is set to A8Bh yielding a default measurement time per phase of

100μs. The length of time to complete a full eye scan is then approximately 128 bits x

SAMPLE_TIME x 2 passes. Two passes are executed by the state machine when checking

arbitrary data to map the left and right portions of the eye separately.

The equivalent bit-error-rate is then defined as at least ERROR_THRESHOLD / (data rate

* SAMPLE_TIME) for phases with errors.

4.12.1.2 Single Timed Measurement

A manual timed measurement can be used to count the number of errors at a single

phase for a pre-defined length of time. The length of the measurement is defined by the

number of bit errors recorded is stored in the ERROR_COUNT bits of the

100

110

120

0.00

0.20

0.40

0.60

0.80

Jitter Amplitude (UI)

HEM Eye Width Measurement vs. Input Jitter

3G, HD Data

SAMPLE_TIME

MEASUREMENT_PREDIVIDER

MEASUREMENT_TIME

() 1 108MHz

()

⁄

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