Fluke 900 - Manual (Page 13)

FLUKE 900 SERVICE MANUAL Theory of Operation
2 Theory of Operation
2.1 General
Major functional blocks of the tester correspond, in general, to physical modules. Shown below is
a diagram of the modules and their interconnections.
The Interface Buffer (IB) acquires and conditions signals from the board under test. It accepts 28
signal channels from an interchangeable clip and, by means of a single threshold setting,
translates them into
ECL digital data for transmission to the High Speed Board.
The Micro Board (MB) controls the operating system, user interface and test parameter storage.
The Micro Board has a Z80 microprocessor running from about 320K of paged memory space.
The software is mainly comprised of interrapt routines that service four 8536 CIO devices. Two
CIOs are on the MB, the "Keyboard" and "Map" devices, while two CIOs are on the HSB, the
"Time" and "Frequency" devices.
The Micro Board sets up the High Speed Board (H3) with the proper configuration for a test
before letting it run at high speed without intervention. The setup of the test proceeds by loading
a series of shift registers with data impropriate for the test to be performed. Four 8 bit registers
are cascaded to make a set of 32 bits in length. Six such sets are located on the H3, two on the IB.
2-1