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System simulation
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The infamous "90/50 rule" states that while about 90% of all
integrated circuits work fine on the chip-tester first time,
only 50% of the same chips actually work in the target system.
That is, the ASICs comply to their specification,
but the specifications in turn are not complete
or fail to reproduce some aspects of the host environment.
Therefore, HADES tries to support System simulation, where the target circuit is simulated together will all its environment, which may contain other digital and analog circuitry, as well as I/O components and even physical entities. For example, the system simulation of a anti-blocking brake controller should include not only the controller and its related circuitry, but also a model of the brake and the road.
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Overview and concepts
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Examples
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Some examples for system simulation within HADES: |
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An ultrasonic range detector built with the PIC16C84 microcontroller,
transmitter/receivers, and alphanumeric LC-display.
The analog components of the complete design are modelled by a
digital adjustable delay line (top right).
Idea and software for this design were published by
EPE online magazine.
The controller creates 40 KHz pulse signals to drive an ultrasonic transmitter. The reflected ultrasonic signals are received by a corresponding sensor, amplified, and fed back to the interrupt logic of the processor. The processor calculates a distance value based on the arrival time of the reflected signal and current temperature, which is displayed on the LCD. |
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A MIDI controller design that demonstrates
system simulation and HW/SW-cosimulation
with the PIC16C84 microcontroller.
Besides the Hades design, the screenshot also includes the
user interface of the processor core with disassembled program memory
and waveforms showing the last MIDI transmission.
The microcontroller is connected to a multiplexed seven-segment display with three digits, a multiplexed keyboard with twelve switches, and a midi-compatible open-drain driver. The software running on the microcontroller scans the keyboard (polling) and generates MIDI program change messages corresponding to the user-selected program number. Note that the controller has to drive the segment lines to display the program number, and to release them during reading of the keypad status. Simulation is only possible due to the usage of the IEEE stdlogic1164 logic model, together with the pullup components on the segment lines. |
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The main schematic for a radio controlled clock,
which decodes the time information broadcast by the
German DCF77 sender near Frankfurt.
With its separate blocks for decoder state machine, decoder
shift registers, and the 'standard' clock circuitry,
this design consists of about 1000 components in
three levels of design hierarchy.
Also, note the behavioral model for the DCF77 sender in the lower left. Not shown in the screenshot is the user interface of the DCF77 component, which allows to specify the date and time to transmit. |
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11.12.99
Impressum
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http://tech-www.informatik.uni-hamburg.de/applets/hades/html/systemsimulation.html |
