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The simpleRTJ is a clean room implementation of
Java Virtual Machine. It differs from other Java VM implementations
not only in the small memory footprint (which is on most
microcontrollers about 18-24KB) but also the way how the class
loading is performed.
On most embedded systems
Java applications will not be frequently updated or reloaded
from the host computers but may require frequent re-starts
(turning power on). To minimize the application start-up
times and to speed up the bytecodes execution the simpleRTJ
executes a pre-linked Java applications. Java application
class files are linked on the host computer. Such generated
application file is then uploaded to the target device for
direct execution by the simpleRTJ.
The simpleRTJ
has been primarily designed to run on the small 8/16 bit
systems with a small amount of memory. However, the simpleRTJ
can also be used on the more powerful devices based on the 32 bit
microcontrollers as it supports linear memory addressing of up
to 16MB. Porting the simpleRTJ is quite
straightforward and in some cases the compilation for the
target device may not require any changes at all to the generic VM
sources.
The simpleRTJ
has been ported to a number of target processors including
MC68302, MC68376/332, 68HC11, 68HC16, 8051XA, various
ARM7/9 derivatives, H8S/2241, STi5512, embedded x86, ZSP200/400/neo, and many others.
simple RTJ Performance
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Executes
pre-linked Java applications which significantly
reduce the start-up times as no dynamic class loading is
required |
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Pre-linked
classes allow VM to execute bytecodes at full speed
without any delays that are otherwise required to
resolve the constant pool symbolic references |
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Efficient
memory and method frames allocation schemes improve
the overall VM performance |
Possible applications
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Smart
cards, smart card readers/writes and terminals |
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Electronic
toys |
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Robotic
controllers and manipulators |
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Small
consumer devices - pagers, cellular phones, etc. |
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Various
embedded control systems |
Download the simpleRTJ
technical
brief (256KB PDF).
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