DIGITAL MODULATION MODE
3-32
Timing
The clock timing sources can be selected between externally and internally derived. The signals
are applied to, or are available, on the appropriate contact of the rear panel AUXILIARY IN/OUT
connector. (For pin-out see 'Auxiliary I/O connector' in Chap. 2.)
Timing selection is as follows:
To select the symbol clock source for parallel operation press the
[Int/Ext Symbol Clk]
key to
toggle between an external input and an internally generated source.
To change the symbol clock polarity press
[Sym Clk Polarity]
to toggle between positive and
negative edge triggering.
For serial data operation, the bit clock source may be selected by pressing the
[Int/Ext Bit Clock]
to toggle between an external clock input and one being generated internally.
To change the bit clock polarity press
[Bit Clk Polarity]
to toggle between positive and negative
edge triggering.
Menu exit
Press [SIG GEN] to return to the
Sig Gen
menu where further selections may be made.
Selecting internal data
Pressing
[Select Internal]
displays the
Internal Data Selection
menu shown in Fig. 3-29.
LOCAL
All 0’s
All 1’s
PRBS
EXIT
PRBS "n"
Value
C0847
Internal Data Selection
Data Source: Pseudo Random
"n" value:
15 - -
[Permitted "n" values are: 2-7, 9, 10, 11, 15]
Fig. 3-29 Digital modulation: Internal data selection menu with PRBS selected
This menu enables the bit stream to be set to
[All 0's]
,
[All 1's]
or
[PRBS]
.
When pseudo random bit stream is selected, the length of the sequence can be entered. To do this,
press the
[PRBS "n" Value]
key and enter an allowed value of n, then terminate by the [enter] key.
Menu exit
Pressing
[EXIT]
returns to the
Data/Timing Control Menu
(Fig. 3-28).