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Logic Analyzer Concepts
The Analyzer Hardware
CPU board
The microprocessor is a Motorola 68EC020 running at 25 MHz. The
microprocessor controls all of the functions of the logic analyzer
including processing and storing data, displaying data, and configuring
the acquisition ICs to obtain and store data.
System memory
The system memory is made up of both read-only memory (ROM) and
random access memory (RAM). Two types of ROM are used. A single
128Kx8 EPROM is used as a boot ROM, and four 512Kx8 Flash ROMs
are configured to provide a 512Kx32 Flash ROM space. One SIMM
socket supports 2-MB, 4-MB, or 8-MB SIMMs.
On power-up, instructions in the boot ROM command the instrument
to execute its boot routine. The boot routine includes power-up
operation verification of the instrument subsystems and entering the
operating system. The CPU searches for the operating system on flash
ROM. Then, if the operating system is in flash ROM, the instrument will
be initialized with the default configuration and await front panel
instructions from you. If the operating system is not in flash ROM, the
CPU accesses the disk drives to see if the operating system is on the
disks.
The DRAM stores the instrument configuration, acquired data to be
processed, and any inverse assembler loaded in the instrument by the
user.
Keypad and knob interface
The front panel keypad is scanned directly from the microprocessor
address bus during the video blanking cycle of the CRT. When a front
panel key is pressed the associated address bits are fed to the data bus
through the pressed key and read by the microprocessor.
The rotary pulse generator (RPG) knob has its own interface. Pulses
and direction of rotation information are directed to the RPG interface.
The microprocessor then reads and interprets the RPG signals and
performs the desired tasks.