Data Acquisition And Processing Subgroup - Keysight Technologies N5221A Service Manual

Theory of Operation
Digital Processing and Digital Control Group Operation
Keypad Assembly
The keypad assembly provides user interface to the analyzer. The front panel
rotary pulse generator (RPG) knob is not electrically connected to the keypad,
but rather provides user inputs directly to the front panel processor.

Data Acquisition and Processing Subgroup

The data acquisition and processing subgroup contain the following
assemblies. See
— A12 SPAM Board (Digital Description)
— A17 CPU Board
— A51 Solid State Drive
A12 SPAM Board (Digital Description)
The A12 SPAM board contains digital and analog circuitry. For analog
descriptions, refer to
The digital signal processor (DSP) receives digitized data from the digital
circuitry of the A12 SPAM board. It computes discrete Fourier transforms to
extract the complex phase and magnitude data from the analog IF signal. The
resulting raw data is written into the main random access memory (RAM). The
data taking sequence is triggered either externally from the rear panel or by
firmware on the A17 CPU board.
A17 CPU Board
The A17 CPU board contains the circuitry to control the operation of the
analyzer. Some of the components include the central processing unit (CPU),
memory (EEPROM, ROM, RAM), bus lines to other board assemblies, and
connections to the rear panel. Some of the main components are described
next:
— CPU
— Main RAM
— Rear Panel Interconnects
CPU
The central processing unit (CPU) is a microprocessor that maintains digital
control over the entire instrument through the instrument bus. The CPU
receives external control information from the keypad, any USB device, LAN or
GPIB, and performs processing and formatting operations on the raw data in
the main RAM. It controls the DSP, the video processor, and the interconnect
port interfaces. In addition, when the analyzer is in the system controller mode,
the CPU controls peripheral devices through the peripheral port interfaces.
Front panel settings are stored in SRAM, with a battery providing at least
five years of backup storage when external power is off.
Keysight N5221A/22A Service Guide
Figure 5-8 on page 5-27.
(including rear-panel interconnects)
"A12 SPAM Board (Analog Description)" on page 5-23.
5-29