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Assembly Descriptions
A3 - Digital I/O Board Assembly
A3 - Digital I/O Board Assembly
The A3 Digital I/O Board assembly is serviced as an assembly only; no component
level repair is supported.
The A3 Digital I/O board assembly performs two important functions:
1. System synchronization
2. RF Preselector Filter hardware control
The A3 Digital I/O board assembly also contains FPGA program code stored on it
that is loaded at boot up. This code is updated, if necessary, when the instrument
software is updated. Interruption of the FPGA update process can result in an A3
Digital I/O board being rendered non-functional, requiring a replacement board
assembly. For more information on updating the N9039A instrument software see
Chapter 9 , "Instrument
Software".
System Synchronization
There are two synchronization pulses generated on this assembly that are required
for the PSA EMI Measurement Receiver system to trigger properly when the
N9039A RF Preselector is being used in the Filter mode. These are rear panel
connections labeled:
• External Trigger Out
• Pulse Trigger 2 Out
These pulsed output signals are used when more than one filter in the N9039A is
used during a given sweep of the PSA. These triggers allow the N9039A to control
the sweep of the PSA in such a way that when the N9039A switches from one filter
to the next the PSA will hold the sweep until the N9039A is properly tuned to the
next filter frequency.
RF Preselector Filter Hardware Control
The A3 Digital I/O board assembly is the only assembly in the N9039A, other than
the A4 Processor board, that is connected to the PCI bus. The A4 Processor board
assembly communicates with the A3 Digital I/O board assembly via the PCI bus,
which in turn communicates with the rest of the RF preselector filter hardware in
the instrument via the Instrument Local Bus (ILB), which the A3 Digital I/O board
assembly contains the controller for.
Chapter 3
95
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Troubleshooting
