Service Guide 12-9
8719ET/20ET/22ET Theory of Operation
8719ES/20ES/22ES Digital Control Theory
RF Network Analyzers
Digital Control Theory
The digital control functional group consists of the following assemblies:
• A1 Front Panel
• A2 Front Panel Processor
• A7 CPU
• A10 Digital IF
• A16 Rear Panel
• A18 Display
• A19 GSP
• A20 Inverter
These assemblies combine to provide digital control for the entire analyzer. They provide
math processing functions, as well as communications between the analyzer and an
external controller or peripherals. A block diagram of the digital control functional group is
located at the end of Chapter 6 , “Digital Control Troubleshooting.”
A1 Front Panel
The A1 front panel assembly provides user interface with the analyzer. It includes the
keyboard for local user inputs, and the front panel LEDs that indicate instrument status.
The front panel knob is not electrically connected to the front panel, but provides user
inputs directly to the front panel processor.
A2 Front Panel Processor
The A2 front panel processor detects and decodes user inputs from the front panel and the
RPG, and transmits them to the CPU. It has the capability to interrupt the CPU to provide
information updates. It controls the front panel LEDs that provide status information.
A7 CPU/A10 Digital IF
The A7 CPU assembly contains the main central processing unit (CPU), the digital signal
processor, memory storage, and interconnect port interfaces. The main CPU is the master
controller for the analyzer, including the other dedicated microprocessors. The memory
includes EEPROM, DRAM, flash ROM, SRAM, and boot ROM.
Data from the receiver is serially clocked into the A7 CPU assembly from the A10 digital
IF. The data taking sequence is triggered either from the A14 fractional-N assembly,
externally from the rear panel, or by firmware on the A7 CPU assembly.
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