Design and Implementation of
Digital Cymometer Based on CPLD
Abstract
With the adoption of the top-down design method and AT89C51 SCMC (Single
Chip Mico Computer) as the master control component of the system ,the circuit test
signalcontrolling ,data operation processing ,keyboard scanning ,and nixie tube
display as well were completed by the digital cymometer.A
CPLD ,EPM7128SLC84-15 ,programmed by VHDL ,realized various sequence
control and count functions .The system is characterized by impact structure ,high
reliability ,high precision ,and wide frequency-test-range .
Keywords
digital cymometer
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complex programmable logic device
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SCMC
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EDA
technology
1 Introduction
The system core called SCMC (Single Chip Mico Computer) emerges constantly
despite the unceasing development of electronic and computer technologies.The
frequency measurement or cycle measurement is usually utilized for testing signals
that use frequency as a parameter. When the tested frequency is relatively
high ,relatively high precision can be available with frequency measurement . When
the tested frequency isrelatively low ,relatively high precision can be a vailable with
cycle measurement . However , neither of them can ensure the measurement precision
in the whole frequency range ,when the range of tested frequency is comparatively
wide .
This digital Cymometer utilizes the advanced EDA technology and top-down
design method . Thus ,the Cynometer implements the equal precision measurement of
the signal frequency range of 0.1 Hz
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50MHz
by AT89C51 SCMC and CPLD
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and also measures pulse width and duty ratio .
Because of the convenience of CPLD programming ,quick speed , high integration ,
and low price , the system research circle is extremely
shortened and the product ratio of performance versus price is improved . The CPLD
chip employs the popular VHDL and achieves all the program design and Download
on the MAX+PlusII software platform . The control portion of SCMC ,programmed
by assemble language precisely sets time , exactly controls startup and closedown of
frequency-test count strobe ,which further ensures measurement precision . System
theory and software & hardware design are introduced below .
2 Equal precision measurement theory
In CPLD ,top-level circuit structure realized by VHDL is shown in figure
1 ,where CONTROL1 is control module of frequency-est ,CONTROL2 is control