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Block Diagram Descriptions
Theory of Operation
3Ć22
Waveform Display RAM
This memory circuitry consists of 65,536 bytes. These bytes contain the
minimum/maximum pairs of values, along with color index and overrange/
underrange information.
Video DigitalĆtoĆAnalog Converter (DAC)
This circuit converts the digital data from the Display IC into analog data for
the A7 CRT Socket board.
The A17 Executive Processor board consists of the:
H Executive processor (EXP)
H Numeric coprocessor circuitry
H Bus buffer circuitry
H Preset circuitry
H Wait state circuitry
H Interrupt controllers
H DMA Controller
See Figure 9Ć11 for a block diagram of this board.
Executive Processor (EXP)
This microprocessor executes firmware routines stored in EPROMS that are
located on the A18 Memory board to control the operation of the CSA 803A.
Along with the numeric coprocessor, the EXP does all data processing not
directly related to generating the display or digitizing the waveform. When
power is first applied to the CSA 803A, the EXP executes local and system
diagnostic tests, which are located in the EPROMs on the A18 Memory
board.
The EXP performs the following functions with three main circuits:
H the clock generator generates the timing signals and synchronized reset
signals for the microprocessor
H the microprocessor reads and writes data, generates addresses for I/O
and memory devices, and generates status signals for the bus controller
H the bus controller interprets the microprocessor's status signals and
generates the necessary bus control signals for the Executive bus
Address decoders, address latches, and data buffers are all support circuits
for I/O operations.
A17 Executive
Processor Board