A4 Cpu Description; Disk Drive; Front Panel Interface; Graphics Controller - Keysight n9020a Service Manual

CPU/Disk Drive Troubleshooting

A4 CPU Description

A4 CPU Description

instrument boot process is described in
Troubleshooting".

Disk Drive

The A5 Disk Drive assembly is contained within the A4 CPU board assembly
and is replaced as an individual assembly. Also, when the A4 CPU board
assembly is replaced the existing A5 Disk Drive assembly will be used.

Front Panel Interface

The instrument USB bus is the electrical interface to the instrument front
panel. One of the USB ports on the host controller hub located on the A4 CPU
board assembly is routed to the A1A2 Front Panel Interface board for this use.
The port is a High Speed USB (2.0) compliant port.

Graphics Controller

The entire graphics subsystem is contained within a single chip, along with the
interface logic to map memory from main system memory for the video RAM.
There are two outputs of the graphics controller that are used by the
instrument. One provides the LCD video data to drive the internal instrument
LCD display and the other supplies the rear panel VGA output.

Power Supply Control

The power control line from the front panel momentary power switch connects
to the A4 CPU board assembly. When the front panel power switch is turned on
the A4 CPU board assembly pulls the PS_ON line to the A6 Power Supply
assembly to a TTL low level, which tells the power supply to turn on. Once the
+12V D, +5.1V D, and +3.35V D supplies are all on and within specification the
A6 Power Supply assembly pulls the PWROK_H line to a TTL high state, which
then causes the A4 CPU board to come out of reset and boot-up.
Outputs from the A4 CPU board assembly also drive the two front panel power
state LEDs.
Provisions have also been made to allow the CPU board to remember which
power state it was in when a power failure occurs. The instrument will return to
the same power state after a power failure.
If the CPU board is suspect in an instrument failure, a full description of the
Chapter 2, "Boot Up and Initialization
306