RF: Connection Control CMU
1100.4903.12 4.70 E-10
The reference signal used is also routed to output REF OUT 1 so that it can be fed
to other instruments as well.
Note:
The header cyclically displays a warning if no synchronization could be achieved
e.g. because of missing or faulty input signal with external synchroni-
zation selected. At the same time, bit no. 6 (RFNL, Reference Fre-
quency Not Locked) is set in the
STATus:OPERation:CMU:SUM1:CMU1 sub-register associated to the
CMU base system and the query [SENSe:]SYNChronize
:FREQuency:REFerence:LOCKed? returns the value ON.
In the case of external synchronization with squarewave signals (TTL) ensure cor-
rect signal matching to avoid reflections. Otherwise, resulting over-
shoots may cause trigger problems at the CMU input. A possible rem-
edy is to use a lowpass filter or an attenuator pad directly at the CMU
input. Correct synchronization may be checked by comparing the sig-
nal REF OUT 1 with the input signal.
This configuration is valid in all CMU function groups.
Caution: The reference frequency is set to Int. (10 MHz) whenever the base
system is reset. After switching back to Ext. (at REF IN) it is necessary
to allow for a setting time (~1 s) before the CMU can synchronize to
the external reference frequency. The delay is avoided by a partial re-
set of all function groups with the exception of the base system.
Remote control
The commands for the reference frequency are part of the CMU base system:
CONFigure:SYNChronize:FREQuency:REFerence:MODE
INTernal | EXTernal
CONFigure:SYNChronize:FREQuency:REFerence <Frequency>
[SENSe:]SYNChronize:FREQuency:REFerence:LOCKed?
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