134 Chapter 8 Analyzing Digital Sources and Cables
GPER? // returns the pixel error rate in errors per billion
GNPT? // returns the number of pixels measured in billions
GCET? // returns the number of bad pixels for R, G, B components
GFED? // returns information about the first error encountered
Analyzing pseudo-random noise from an external source
The following example tests an HDMI/DVI transmit device’s pixel data using
pseudo-random noise generated by an external source.
To analyze pseudo-random noise from an external source:
1. Connect the DVI or HDMI cable between the receive connector on the generator and
the output interface on the device under test.
2. Using a terminal emulator, establish a terminal connection with the generator. Refer to
“Setting up a terminal connection with the generator” on page 14.
3. Enter the following commands to configure the generator to output a digital signal
(HDMI or DVI):
SROP 2 4
This removes analog friendly mode and configures the generator to output either a DVI
or HDMI signal depending on the interface hardware the generator is equipped with
(DVI or HDMI).
4. (optional) Enter the following commands to set the status display mode:
SROP 8
5. Enter the following commands to configure the pseudo-random noise parameters.
PNSF 1 // selects external timing source for pseudo-random noise
PNST 1 // specifies QDI-BCM algorithm
TMAU // initiates measurement of timing from external source
PNSA 1 // sets pseudo random noise to be calculated each pixel
PNSM 0 // sets pseudo random noise test to run in auto mode
PNSP 100 // sets pseudo-random noise for 100 “multi-shots”
PNAU // loads the generator with the pseudo-random noise settings
Note: The test will stop automatically if configured to run in the single or multi-shot
mode. If you initiate the test in the continuous mode, you will have to enter a carriage
return to halt the test after PNAU is invoked.
6. Enter the following commands to view the results of the test.
GPER? // returns the pixel error rate in errors per billion
GNPT? // returns the number of pixels measured in billions
GCET? // returns the number of bad pixels for R, G, B components
GFED? // returns information about the first error encountered
Testing the analyzer
The following example verifies the analyzer’s pseudo-random noise analysis capability.