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System Functional Overview
Theory of Operation
3Ć4
After the user requests an operation (with a front panel control for instance),
the Executive Processor (EXP) directs the CSA 803A to perform this operaĆ
tion. Another primary function of the EXP is to execute diagnostic SelfĆTests
on the instrument when poweringĆon or at the user's request. To control
operations, the EXP controls and monitors the other circuit boards sharing
the executive system bus. Through the executive bus boards, the EXP also
indirectly controls all other instrument boards. The EXP generates comĆ
mands and status signals to control onĆboard devices and I/O devices, such
as GPIB and RSĆ232ĆC interfaces, that help process data and help control
the rest of the instrument.
The memory management unit (MMU) arbitrates requests for access to the
Waveform Memory from the following three sources:
H the EXP
H the Time Base/Controller
H the display system
This arbitration allows all three systems transparent access to the Waveform
Memory.
Waveform Memory is shared among the following processors:
H the EXP
H the Display
H the Time Base/Controller
While the main function of the Waveform Memory is the storage of waveform
data and waveform related information, the shared memory is also used to
pass messages between the Executive, Display, and Time Base/Controller
processors. Eventually, all acquired waveforms are transferred from the
Acquisition system memory to the Waveform Memory for display.
Executive Processor
Block
Memory Management
Unit Block
Waveform Memory
Block