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Trigger Detection
The trigger event used to start a measurement can be generated in five different
ways:
•
Software trigger
•
External
•
ADC threshold
•
Log-magnitude
•
Immediate
All triggering modes support slope selection. In ADC or log-magnitude mode the
trigger threshold can be specified with hysteresis to prevent noise-generated
triggers of the wrong slope. Log-magnitude triggering is based on the magnitude of
the complex signal after zooming and filtering.
For external mode, a trigger signal must be supplied at the "Ext Trigger" connector
on the front panel. Any signal with a sharp rising or falling transition greater than
100 mV (i.e. TTL or ECL) can be used as an external trigger source.
Any E1437A module can trigger other E1437A modules using a shared sync line on
the VXI backplane. This SYNC line can be extended to other mainframes by
connecting a "Sync" SMB connector to a "Sync" SMB connector on a E1437A in the
second mainframe. All modules in a synchronous system are triggered on the same
ADC sample.
The E1437A hardware samples the trigger source once every sample clock, so the
trigger condition must be present for at least one sample clock in order to be
recognized.
Control Registers
The E1437A module is controlled by firmware using registers mapped into the 16-bit
VXI address space. There are 24 writable and 18 readable registers, each has 16 bits.
The control registers are not user accessible.
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E1437A User's Guide
Module Description
6-9
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