Keysight Technologies 34970A Service Manual

Also see for 34972A: Manual

Contents

Keysight Technologies 34970A Service Manual Manual pdf 128 page image

5 Theory of Operation128 Keysight 34970A/34972A Service GuideFloating LogicUnless otherwise noted, components in this discussion are located on the A1circuit assembly (34970-66501).The floating common logic controls the operation of the entire instrument. Allmeasurement control and remote interface command interpretation is performedin the main controller, U205. The front panel controller, the I/O controller, and allof the plug-in module controllers, act as slaves to U205. The floating commonlogic is comprised of the main controller U205, custom ASIC U209, calibrationmemory U201, 12 MHz clock oscillator U204, and microprocessor supervisorU104.The microprocessor supervisor U104 performs the following functions:– Monitors the regulated 5V floating supply and generates the reset signal formain controller U205 when the voltage drops below operating levels.– Monitors the unregulated side of the 5V floating supply in order to generate anearly warning signal (PWRFAIL) when power is lost.– Provides automatic switch over to the battery BT101 for the +5V_NV supplywhen the 5V_FLT supply drops below the battery voltage.– Blocks the main controller’s write signal (WR_N) while the 5V_FLT supply isbelow operating level.