Front Panel Subgroup - Keysight Technologies N5221A Service Manual

Theory of Operation
Digital Processing and Digital Control Group Operation

Front Panel Subgroup

The front panel subgroup contains the following assemblies:
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A1 Front Panel Display Board
The A1 front panel display board detects and decodes user inputs from the
keypad assembly and front panel knob, and transmits them to the A17 CPU
board by way of the A14 system motherboard. It also decodes video data from
the video processor on the A17 CPU board and supplies this to the A3 display
assembly. Power from the power bus on the A14 system motherboard is
buffered and routed to the keypad assembly and the A3 display assembly. All
data and power signals are routed through a single cable connector to the A14
system motherboard.
The A1 front panel interface board also includes a speaker that emits the audio
signals received from the A17 CPU board.
A2 USB Board
This board provides four universal serial bus (USB) jacks that are industry
standard 4-pin connectors allowing multiple USB devices to be connected to
the analyzer's front panel.
A3 Display Assembly
The A3 display assembly contains an 10-inch LCD with associated drive
circuitry and backlight inverter. Two cables between the A3 display assembly
and the A1 front panel display board provide all necessary power and data for
normal operation. The two cables are:
1. A cable to the inverter that supplies buffered power.
2. A cable to the display circuitry that supplies decoded data from the video
• digital TTL horizontal sync
• digital TTL vertical sync
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A1 Front Panel Display Board
A2 USB Board
A3 Display Assembly
Keypad Assembly
processor on the A17 CPU board and the necessary drive circuit power.
The video data received from the A17 CPU board includes the following:
• digital TTL red video
• digital TTL green video
• digital TTL blue video
• blanking
• data clock
Keysight N5221A/22A Service Guide