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Synchronizing changes in multi-module systems
Multi-module systems require special treatment with respect to timing of frequency and filter
changes. Center frequency changes may involve synchronizing the local oscillators of all modules
in a system. Digital filter changes in multi-module systems require that the decimation counters
be synchronized.
Calling the following functions voids synchronized multi-module setups:
age1439_clock_setup and related low-level clock setup functions
age1439_clock_recover
age1439_input_autozero
age1439_input_range_auto
age1439_self_test
age1439_state_recall
Special considerations apply to the measurement loop.
module systems" on page
Synchronous digital filter changes
In multi-module systems where synchronous sampling is required, the decimation counters in all
the modules must be synchronous with each other. This condition can be forced by preparing each
module in the system in advance. Any measurement in progress is terminated at this time and the
module is placed in the Idle state. After each module is prepared, the next sync line transition
causes the digital decimation counter to be reset and started at the same time. Once this is done,
the decimation counters stay synchronized as long as the same ADC clock is used.
If you also intend to change the center frequency along with the digital filters, you should
synchronize the digital filters first. Otherwise, the center frequency phase becomes
unsynchronized when the digital filters are changed.
Synchronous center frequency changes
In multi-module systems you may prepare each module in advance of a frequency change, then
perform the change synchronously by asserting the Sync line. This preserves the phase
relationship of the local oscillators for all modules in the system. Certain special considerations
apply to multi-module frequency changes:
•
If all modules in a system are in the Idle state when the Sync line transition occurs, the LO
frequency is updated and the next measurement is armed.
•
If all modules are in the measurement state in continuous mode when the Sync line transition
occurs, the LO frequency is synchronously updated, and the measurement continues.
•
In continuous mode, care must be taken to assure that all modules are in the same state, either
the Idle state or the Measure state, before the Sync line transition occurs, otherwise some
modules re-arm while others continue the current measurement.
•
In block mode, it is simplest to keep Forced Idle asserted during the Sync line transitions to
keep all the modules in the Idle state.
•
If you also intend to change the digital filters along with the center frequency, you should
synchronize the digital filters first. Otherwise, the center frequency phase becomes non-
synchronized when the digital filters are changed.
24.
Using the Agilent E1439
Managing multiple modules
See "The measurement loop in multi-
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