Agilent 34970A/34972A Data Acquisition / Switch Unit

Chapter 5 Theory of Operation
Floating Logic
Floating Logic
Unless otherwise noted, components in this discussion are located on the
A1 circuit assembly (34970-66501).
The floating common logic controls the operation of the entire
instrument. All measurement control and remote interface command
interpretation is performed in the main controller, U205. The front panel
controller, the I/O controller, and all of the plug-in module controllers,
act as slaves to U205. The floating common logic is comprised of the main
controller U205, custom ASIC U209, calibration memory U201, 12 MHz
clock oscillator U204, and microprocessor supervisor U104.
The microprocessor supervisor U104 performs the following functions:
• Monitors the regulated 5V floating supply and generates the reset
signal for main controller U205 when the voltage drops below
operating levels.
• Monitors the unregulated side of the 5V floating supply in order to
generate an early warning signal (PWRFAIL) when power is lost.
• Provides automatic switch over to the battery BT101 for the +5V_NV
supply when the 5V_FLT supply drops below the battery voltage.
• Blocks the main controller’s write signal (WR_N) while the 5V_FLT
supply is below operating level.
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