Emulator
• Device that allows user program written for one
kind of computer system to be run on another
system.
• A micro programmed control provides a simple,
flexible & inexpensive control of a computer.
• A micro programmed control also provides
flexibility in handling of resources & allows
implementation of diverse classes of instruction.
Necessity of Emulator
• A user can create his own instruction set by using
micro programs.
• e.g. if we add instruction set of C2 computer to C1
computer, so C1 emulates C2.
• All programs written for C2, now can run on C1 also.
• It is very useful as it allows replacement of absolute
equipment with more up to date machines.
• If the replacement computer fully emulates the original
one, then no software changes have to be made to
run the existing programs.
• Emulation is easier when the machine involved have
similar structure.
• It can be a h/w, micro programs & s/w added to
computer C1 so that it can execute programs written
for a different computer C2.
• If only s/w is used for implementing then it is
simulation.
• h/w of emulator consist of control circuitry, memory to
store the trace data after each instruction executes &
a cable with a plug at the end.
• Emulator contains microprocessor which will run your
test programs.
• The s/w of the emulator is similar to a monitor program
or debugger program.
• Emulator can debug, examine & change the contents
of register & memory locations.
In – Circuit Emulator
• It is an essential part of the design process for
microprocessor based products.
• It is the execution of a prototype s/w program in
prototype h/w under the control of a s/w development
system.
• To perform an in-circuit emulation, the microprocessor
is removed from the prototype design boaed & a 40 –
pin cable from in-circuit emulator is plugged into the
previously occupied by the microprocessor.
• It performs all the function of the replaced
microprocessor.
• In addition, it allows the prototype h/w to share all its
resources, such as s/w, memory & I/Os.
• It provides window for looking into the dynamic, real-
time operation of the prototype hardware.
Emulation Process
• To test sub systems ( such as I/O & memory) using an
in-circuit emulator, the minimum prototype h/w
required is a 40 pin microprocessor socket, without the
microprocessor, & a power supply.
• Features of In-circuit Emulator :
• It is a s/w or h/w trouble shooting instrument.
• It can be stand alone unit or part of a s/w development
system.
• A small can be entered directly into the emulator, or a
program can be transferred into the emulator from a
host computer system through an RS-232 serial link.
• Once a program is loaded, a user can interact with the
emulator through its keyboard or a terminal.
• The emulator has its own s/w commands to perform
various debugging functions.
Capabilities of Emulator
• Down Loading : facilities are provided to transfer
programs between a s/w development system or a
host computer & in-circuit emulator.
• Resource Sharing : system being tested to share its
memory & I/O parts. Uses memory & I/O mapping.
• Debugging tools : (1). Break Points
(2). Mnemonic Display.
(3). Real-Time Trace : RAM is used as a buffer to store
the last several bus operations, & these can be
displayed on the screen. Display is like snap shot of
all the bus operations in real time.
• In-line Assembly : allows the user to change
data or instructions while the software is in the
in-circuit emulator.
• Disassembly : after instructions are changed
in the in-circuit emulator, this facility can write
mnemonics in software.
• Register Display : this display the register
contents after the execution of instructions.
• ICE 85 control board.
Benefits
• Emulators maintain the original look, feel, and behavior of the
digital object, which is just as important as the digital data itself.
• Despite the original cost of developing an emulator, it may
prove to be the more cost efficient solution over time.
• Reduces labor hours, because rather than continuing an
ongoing task of continual data migration for every digital object,
once the library of past and present operating systems and
application software is established in an emulator, these same
technologies are used for every document using those
platforms.
• Many emulators have already been developed and released
under GNU General Public License through the open source
environment, allowing for wide scale collaboration.
Obstacles
• Intellectual property - Many technology vendors
implemented non-standard features during program
development in order to establish their niche in the
market, while simultaneously implementing ongoing
upgrades to remain competitive.
• While this may have advanced the technology industry
and increased vendor’s market share, it has left users
lost in a preservation nightmare with little supporting
documentation due to the proprietary nature of the
hardware and software.
• Copyright laws are not yet in effect to address saving
the documentation and specifications of proprietary
software and hardware in an emulator modu