Agilent Technologies VXI E1439 User Manual
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Using the Agilent E1439
The measurement loop
Modules programmed for block mode operation assert the Sync line until a complete block of
data, including any pre-programmed pre- or post-trigger delay, has been collected and is available
to the I/O port. The module then releases the Sync line. The module returns to the Idle state when
the block of data has been collected.
In continuous mode, a module releases sync immediately but moves to the Idle state only if
explicitly programmed to do so or if the FIFO data buffer overflows because data cannot be read
from the I/O port fast enough.
The measurement loop in multi-module systems
The following rules generally apply to transitions between states when multiple modules share a
Sync signal:
•
If any one module asserts the Sync line, a synchronous state transition occurs for all modules
in a system.
•
All modules in a system must have released the Sync line in order to bring about a
synchronous transition to Trigger state.
•
In block mode, each module releases the Sync line after its block of data has been collected.
Immediately upon entering the Measure state in continuous mode, each module releases the
Sync line. It continues to collect and output data until it is programatically signaled to stop or
until the FIFO overflows. With the Sync line released it is then possible to change the center
frequency for one or multiple modules without interrupting the measurement.
“Synchronizing changes in multi-module systems” on page 39
•
A module may be programmed explicitly to inhibit its transition to the Arm state despite Sync
transitions.
•
In addition to controlling the progression through the four module states, the Sync signal is
used to synchronize the decimation counters and local oscillators of multiple E1439 modules.