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E1437A
ASCII Overview and Commands
NOTE
When the SYNC line is asserted, it will remain asserted for an adequate number
of ADC clock cycles to ensure that the signal effect will have propagated to all
the modules in the system. You can determine when the command is completed
by looking as the Sync/Idle Complete bit in the Status Register.
Comments:
See The Measurement Loop section for details on how a measurement progresses
through the four states.
Special conditions prevail during the Measure state. If programmed for block mode
operation in the Measure state, the module will assert the SYNC signal (regardless of
the MEAS:CONTROL sync parameter setting) until a complete block of data has
been collected and is available to the I/O port. When the shared SYNC signal is
released, indicating that all block mode data collection is finished, all block mode
modules move synchronously to the idle state. In continuous mode the module
releases the SYNC signal immediately after moving into the measure state. This
allows the MEAS:CONTROL command to manipulate the SYNC signal to cause
synchronous changes to LO frequency while a continuous measurement is in
progress. In continuous mode a module moves to the idle state only if explicitly
programmed to do so or whenever the FIFO data buffer overflows.
In addition to controlling the progression through the four module states, the SYNC
signal is used to allow for synchronizing the decimation counters and local
oscillators of multiple E1437 modules. This is done by calling FILTER:SYNC and/or
FREQUENCY:SYNC prior to asserting SYNC with MEAS:CONTROL. This is normally
done with the module in the IDLE state; however, the center frequency can also be
changed in the Measure state with FREQUENCY:SYNC if the modules are all
programmed for continuous (non-block mode) data collection.
If all modules in a multi-module system are in the idle state when the
MEAS:CONTROL sync parameter is asserted, the LO frequency will be updated and
the next measurement will be armed. If all modules are in the measurement state in
continuous mode, the LO frequency will be synchronously updated, and the
measurement will continue. In continuous mode care must be taken to ensure that
all modules are in the same state, either the idle state or the measure state, before
using MEAS:CONTROL to assert SYNC. Otherwise some modules will re-arm while
others will continue the current measurement. In block mode the sync assertion will
be ignored unless all modules are currently in the idle state.
In the case of systems made up of multiple mainframes you must be aware that only
modules in mainframe A may assert sync. Any sync asserted in other mainframes is
ignored.
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MEAS:CONTROL
command
5-39
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