If you buy some RTOS,what are the features you look for in ? Why is java mostly used in embedded systems?What is the need for DMAC in ES?

-Deterministic operating system having guaranteed worst-case interrupt latency and context-switch times.-Documentation providing for the minimum, average, and maximum number of clock cycles required by each system call-Interrupt response times should be very minute.-Context switch time should be very low.-Compatibility with several plugin devices.- Overall it should be very reliable

Java was mainly designed and conceputalised for code that can work on different platforms without any hassles and also for being secure enough so as to not harm or corrupt other modules of code.Features like exception handling,simple syntax and Automatic Garbage collection all work in its favour as the language for use in ES's.Also that it is widely used in the form of Java applets makes it very popular confining it to the limits of JVM.It is Dynamic in nature.Its use is also being exploited in enterprise systems in the form of J2EE ,J2SEJ2ME in case of mobile applications.

Direct memory access is mainly used to overcome the disadvantages of interrupt and progam controlled I/O.DMA modules usually take the control over from the processor and perform the memory operations and this is mainly because to counteract the mismatch in the processing speeds of I/O units and the procesor.This is comparatively faster.It is an important part of any embedded systems,and the reason for their use is that they can be used for bursty data transfers instead of single byte approaches.It has to wait for the systems resources such as the system bus in case it is already in control of it.

 

 

nfinite Loops are those program constructs where in there is no break statement so as to get out of the loop, it just keeps looping over the statements within the block defined.Example: While(Boolean True) OR for(;;);{//Code} - Embedded systems need infinite loops for repeatedly processing/monitoring the state of the program. One example could be the case of a program state continuously being checked for any exceptional errors that might just occur during run time such as memory outage or divide by zero etc.,- For e.g. Customer care Telephone systems where in a pre-recorded audio file is played in case the dialer is put on hold..- Also circuits being responsible for indicating that a particular component is active/alive during its operation by means of LED's.   How does combination of functions reduce memory requirements in embedded systems? - The amount of code that has to be dealt with is reduced thus easing the overhead and redundancy is eliminated in case if there is anything common among the functions.- Memory allocation is another aspect that is optimized and it also makes sense to group a set of functions related in some way as one single unit rather than having them to be dispersed in the whole program.- In case of interactive systems display of menu list and reading in the choices of user's could be encapsulated as a single unit.