Technical data

80 Agilent U7232A DisplayPort Electrical Performance Compliance Test Application
9 Source Pre-Emphasis Level Differential Tests (Normative & Informative)
Source Pre-Emphasis Level Differential Tests
This test evaluates the effect of pre- Emphasis on the source waveform by
measuring the peak differential amplitude and assuring the accuracy of the
pre- Emphasis setting. (Reference: Table 3.10 VESA DisplayPort Standard).
The source can apply pre- Emphasis to the waveform in order to overcome
the harmful effects caused by such things as system losses through pc
boards, connectors, and cables. The standard stipulates the relative
magnitude to overcome specific losses. Because pre- Emphasis is
negotiated, two units with substantially different degrees of pre- Emphasis
may be seen as non- interoperable under certain conditions. This test
ensures that the system loss or pre- Emphasis budget is obeyed.
Tests must be made on all bit rates supported with pre- Emphasis for all
differential voltage swings supported using a test pattern of PRBS 7. The
following equation is used to calculate the pre- Emphasis result:
where:
V
Hpe
= the high voltage value is measured using the histogram modes
at the top for transition eyes.
V
Lpe
= the low voltage value is measured using the histogram modes
at the top for transition eyes.
V
Hnope
= the high voltage value is measured using the histogram modes
at the top for non- transition eyes.
V
Lnope
= the high voltage value is measured using the histogram modes
at the top for non- transition eyes.
Test P ro ce du re
1 Start the automated testing application as described in “Starting the
DisplayPort Electrical Performance Compliance Test Application" on
page 22.
2 Connect the W2641A test fixture or other appropriate fixture to the
device under test (DUT).
3 If you are using one connection, connect the probe to one channel. If
you are using two connections, connect the two probes to two channels
Pre-emphasis Result 20
V
Swingpe
V
Swingnope
---------------------------
⎝⎠
⎜⎟
⎛⎞
log=
V
Swingpe
V
Hpe
V
Lpe
–()=
V
Swingnope
V
Hnope
V
Lnope
–()=