R&S SMJ100A, Operating Manual

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Instrument Function
R&S
®
SMJ100A
320 Operating Manual 1403.7458.32 ─ 14
External serial data
The following diagram illustrates the timing ratios between data and clock when serial
data is being supplied from an external source and an external reference clock is being
used.
Figure 5-22: External serial data and external symbol clock - 3 bits/symbol with high and low active
symbol clock for marking the LSB. The data and the symbol clock must change state
simultaneously. The setup time (tsetup) and hold time (thold) can be found in the data
sheet.
A bit clock is generated from the externally supplied symbol clock and is used for read-
ing the serial data into the R&S
SMJ. The active edge of this bit clock is located ahead
of the symbol clock.
External parallel data
The following diagram illustrates the timing ratios between data and clock when paral-
lel data is being supplied from an external source and an external reference clock is
being used.
Figure 5-23: External parallel data with high and low active external symbol clock. The setup time
(tsetup) and hold time (thold) can be found in the data sheet.
The R&S SMJ uses the externally supplied symbol clock to generate an internal sym-
bol clock that defines the sampling points at which the parallel data is read into the
R&S
SMJ. These sampling points are also located a little ahead of the external symbol
clock.
External Clock and Internal or External Asynchronous Data
If the modulation data is generated internally or supplied asynchronously from an
external source, clock generation in the R&S
SMJ can be synchronized on an external
symbol clock, or a multiple thereof, which is fed in on the CLOCK connector (front
panel). Synchronization can be based on the rising edge or falling edge according to
choice. The maximum permissible multiple symbol clock can be found in the data
sheet.
Baseband Signal - Baseband Block