Keysight EXG and MXG X-Series Signal Generators User’s Guide 423
Using the N5102A Digital Signal Interface Module for N5172B/82B with Option 003/004 and
653/655/656/657
Clock Timing
— Internal: generated internally in the interface module (requires an external reference)
— External: generated externally through the Ext Clock In connector
— Device: generated externally through the Device Interface connector
The clock source is selected using the N5102A module UI on the signal generator, see Figure 17-2.
Figure 17-2 Clock Source Selection
When you select a clock source, you must let the N5102A module know the frequency of the clock
signal using the Clock Rate softkey. In the internal clock source mode, use this softkey to set the
internal clock rate. For device and external clock sources, this softkey must reflect the frequency of
the applied clock signal.
When the clock source is Internal, a frequency reference must be applied to the Freq Ref connector.
The frequency of this applied signal needs to be specified using the Reference Frequency softkey,
unless the current setting matches that of the applied signal.
The selected clock source provides the interface module output clock signal at the Clock Out and
the Device Interface connectors.
Common Frequency Reference
The clocking flexibility of the digital signal interface module allows the setting of arbitrary clock
rates for the device under test. In general, the clock rate inside the signal generator will be different
from the interface module clock rate, so the interface module performs a rate conversion. An
important aspect of this conversion is to have accurate clock rate information to avoid losing data.
The module relies on relative clock accuracy, instead of absolute accuracy, that must be ensured by
using a single frequency reference for all clock rates involved in the test setup. This can be
implemented in various ways (see the five drawings in Figure 17-3 on page 424), but whatever way
it is implemented, the clock inside the signal generator must have the same base frequency
reference as the clock used by the device under test.
Signal Generator Frequency Reference Connections
When a frequency reference is connected to the signal generator, it is applied the REF In rear panel
connector.
Internal clock source
selection: Set the frequency of
the applied reference signal.
External and Device
selection:
Set to match the clock rate
of the applied clock signal
internal selection: Set the
internal clock rate.
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