31-05-2012, 02:13 PM
VHDL
VHDL.docx (Size: 20.03 KB / Downloads: 34)
Abstract
—This article describes design of the 8-bit asynchronous
microcontroller simulation model in VHDL. The model is created in
ISE Foundation design tool and simulated in Modelsim tool. This
model is a simple application example of asynchronous systems
designed in synchronous design tools. The design process of creating
asynchronous system with 4-phase bundled-data protocol and with
matching delays is described in the article. The model is described in
gate-level abstraction.
The simulation waveform of the functional construction is the
result of this article. Described construction covers only the
simulation model. The next step would be creating synthesizable
model to FPGA.
Keywords—Asynchronous, Microcontroller, VHDL, FPGA.
INTRODUCTION
HIS article has arisen at the beginning of research of the
asynchronous systems properties. The goal of the research
is the simulation of asynchronous systems by using ordinary
design tools (VHDL) and ordinary target platforms (FPGA).
At the beginning it started with asynchronous registers and
combinational blocks. Then it leads to more complex
structures like the microcontroller.
At first a simple controller without external ports and
storage RAM for data was designed. Features of the simple
controller will be explored and compared with classic
synchronous microcontrollers by simulating and following
implementation of the asynchronous circuit.
The next, introductory chapter will explain the
asynchronous system theory. The basic use of bundled-data
protocol and his VHDL code is shown in this chapter. The
third chapter contains the microcontroller design itself.
Following chapter refers to results of the simulation. The
article ends with conclusion.
ASYNCHRONOUS THEORY
Synchronous logical systems are used in most cases. But
the benefits of asynchronous circuits are left unnoticed.
Among the benefits are the speed, modularity, low
consumption and less electromagnetic emission. No global
control, such as clock in synchronous circuits, is here. Every
module has its own control and it communicates with each
other neighboring module. Only operating modules are active.
M. Kovac is with the Radioelectronics Department, Faculty of Electrical
Engineering and Communication, Brno University of Technology, Brno,
Czech Republic (e-mail: xkovac03[at]stud.feec.vutbr.cz).
Operation speed depends only on the physical properties of
semiconductor. No worst-case like in synchronous system is
estimated here.
On the other side asynchronous systems have also
disadvantages, namely the design complexity and lack of
automated design tools.
Asynchronous systems don’t have any global control, but
they communicate locally with each other. This
communication is called handshaking. There are two basic
handshaking protocols: bundled-data and dual-rail. In the
bundled-data protocol the data are packed together.
VHDL.docx (Size: 20.03 KB / Downloads: 34)
Abstract
—This article describes design of the 8-bit asynchronous
microcontroller simulation model in VHDL. The model is created in
ISE Foundation design tool and simulated in Modelsim tool. This
model is a simple application example of asynchronous systems
designed in synchronous design tools. The design process of creating
asynchronous system with 4-phase bundled-data protocol and with
matching delays is described in the article. The model is described in
gate-level abstraction.
The simulation waveform of the functional construction is the
result of this article. Described construction covers only the
simulation model. The next step would be creating synthesizable
model to FPGA.
Keywords—Asynchronous, Microcontroller, VHDL, FPGA.
INTRODUCTION
HIS article has arisen at the beginning of research of the
asynchronous systems properties. The goal of the research
is the simulation of asynchronous systems by using ordinary
design tools (VHDL) and ordinary target platforms (FPGA).
At the beginning it started with asynchronous registers and
combinational blocks. Then it leads to more complex
structures like the microcontroller.
At first a simple controller without external ports and
storage RAM for data was designed. Features of the simple
controller will be explored and compared with classic
synchronous microcontrollers by simulating and following
implementation of the asynchronous circuit.
The next, introductory chapter will explain the
asynchronous system theory. The basic use of bundled-data
protocol and his VHDL code is shown in this chapter. The
third chapter contains the microcontroller design itself.
Following chapter refers to results of the simulation. The
article ends with conclusion.
ASYNCHRONOUS THEORY
Synchronous logical systems are used in most cases. But
the benefits of asynchronous circuits are left unnoticed.
Among the benefits are the speed, modularity, low
consumption and less electromagnetic emission. No global
control, such as clock in synchronous circuits, is here. Every
module has its own control and it communicates with each
other neighboring module. Only operating modules are active.
M. Kovac is with the Radioelectronics Department, Faculty of Electrical
Engineering and Communication, Brno University of Technology, Brno,
Czech Republic (e-mail: xkovac03[at]stud.feec.vutbr.cz).
Operation speed depends only on the physical properties of
semiconductor. No worst-case like in synchronous system is
estimated here.
On the other side asynchronous systems have also
disadvantages, namely the design complexity and lack of
automated design tools.
Asynchronous systems don’t have any global control, but
they communicate locally with each other. This
communication is called handshaking. There are two basic
handshaking protocols: bundled-data and dual-rail. In the
bundled-data protocol the data are packed together.