Technical data

114 Agilent U7232A DisplayPort Electrical Performance Compliance Test Application
13 Source Spread Spectrum Clocking (SSC) Differential Tests (Normative & Informative)
Source Spread Spectrum Clocking (SSC) Differential Test
Spread Spectrum Modulation Frequency (Normative)
The spread spectrum modulation frequency evaluates the frequency of the
SSC modulation and validates if it falls with specification limits.
The SSC frequency will be evaluated at the highest bit rate the transmitter
supports. Tests shall be performed on a PRBS 7 signal, with SSC enabled.
An evaluation of at least 10 full SSC cycles is required (Mean value
reported). As SSC is mandatory, the reported result must be the mean of
ten measured with maximum values from the range of SSC modulation
deviation.
Spread Spectrum Modulation Deviation (Normative)
The spread spectrum modulation deviation evaluates the range of SSC
down- spreading of the transmitter signal in PPM. This requires the device
[the device must] operate in the region of 0 to - 5000 PPM. The SSC
Modulation Deviation will be evaluated at the highest bit rate the
transmitter supports. Tests shall be performed on a PRBS 7 signal, with
SSC enabled.
An evaluation of at least 10 full SSC cycles is required (Mean value
reported). As SSC is mandatory, the reported result must be the mean of
ten measured with maximum values from the range of SSC modulation
deviation.
The value reported as the result must be the single total range value
relative to nominal of the SSC modulation deviation, using the equation
below, where "Min" is the mean of 10 recorded values of the minimum
peaks.
Calculate deviation = (Measured Min - Nominal)/Nominal * 1e6 ppm
Deviation HF Variation (Informative)
The deviation HF variation verifies SSC profile that does not include any
frequency deviations which would exceed 1250 ppm/µSec.
Spread spectrum clocking demands that the sink receiver tracks the
modulated frequency of the source link rate while maintaining clock/data
phase tracking. This test measures the range of frequency deviation with
the source SSC enabled. If this range exceeds specification, the ability of
the sink to frequency and phase track may be impaired, possibly causing
data recovery errors and non- interoperability with a compliant receiver.