Agilent Technologies DSOX4USBSQ USB 2.0 Manual de Serviço descarregar pdf (Página 21)

Device Signal Quality Testing 2

DSOX4USBSQ USB 2.0 Signal Quality Analysis Application Electrical Testing Notes 21

7 Press the Signals softkey. In the USB Signal Quality Signals Menu:

a Press the Test Connection softkey and select whether you are using a

Single-ended (with SMA cables) or Differential probe connection.

b If you are using a differential connection, press the Source softkey

and select the analog input source channel connected to the

differential probe.

If you are using a single- ended (SMA cables) connection, press the

DP SMA softkey and select the analog input source channel connected

to the D+ signal. Then, press the DN SMA softkey and select the

analog input source channel connected to the D- signal.

On 4- channel oscilloscopes, you are forced to use different channel

pairs for the D+ and D- signals. This provides the maximum sample

rate. (Channels 1 and 2 are one pair and channels 3 and 4 are the

other pair.)

Hi- Speed tests using single- ended SMA cable connections are not

supported on 2- channel oscilloscopes because the sample rate does

not meet the required 5 GSa/s.

c Press the Test Type softkey and select Near-end or Far-end.

The terms "near-end" and "far- end" are based on which end of the

cable the test fixture is attached in relation to the device being

tested. The point where measurements are made dictates what eye

template is used.

8 Press the Auto Setup softkey to automatically set up the oscilloscope for

the selected test.

For optimal test results, you can make adjustments to the auto setup.

Generally, you want one packet of data, plus the time of one bit on

each end, across the oscilloscope's display. Also, vertical scale and

offset should be adjusted so that the signals take six vertical divisions

without being clipped.

You should see the transmitted test packet on the oscilloscope as below.

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 85 86

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Agilent Technologies DSOX4USBSQ USB 2.0 Manual de Serviço Página 21