Real-Time Operating System (RTOS)

RTOS might be having 10k memory, might not fragmentation

problem, and the largest hole available to user might be

lesser than 5k, this condition might be one of the reason

for NULL error.

Not sure what this question is. But looks like the question

is: Why 4GB addressing space available in Linux. Well, the

simple answer is it can address so much of memory with

available 32 address lines. 2 ^ 32 = 4 GB.

Adv:

1) Supports various types of processor platforms

2) Possible to Customize the Kernel and can reduce its size

(upto ~300KB kernel size)

3) Especially for the embedded device platforms

Disadv:

1) Process limits, max. 32 process at a time in WinCE 5.0

2) Limited space allocation for each processes, 32MB/each

process

Well there is nothing to related with limited H/w I believe,

Because MFC is just a collection classes designed using the

Windows APIs , to provide ease of use.

So the proper answer may Be...

To design any application on mobile.. We have very limited

APIs which user can directly used. Generally in Embedded

system (even in Soft RTOS also ) , if application design

using less ( comfort )layer like MFC ( and other if it is

there :) ),then your aplication would be more efficient.

That's why even today's era... The application written in

Assembly is the most efficient application then others.

speciality in the sense ...

1) number of processes supported by wince 5.0 is more

than wince 4.0

2) memory mapping might be varying.

there are four levels in Win CE architecture.

They are

1)Hardware layer

2)OEM layer

3)OS layer

4)Application layer

MSFT standard SDK's are,

1. Windows Mobile for Smartphone = Windows Mobile Standard.

2. Windows Mobile for Pocket PC = Windows Mobile Classic.

3. Windows Mobile for Pocket PC Phone Edition = Windows

Mobile Professional.

Normal OS wince

drivers runs under User space(part of device manager)

kernel space

cannot be customized customized for embedded application

for embedded application like mobile phones,thin client...

(exception linux)

kernel - monolithic kernel- micro kernel

In the name "Windows CE," the letters "CE" are not an

abbreviation for anything, but rather they imply a number

of the precepts around which Windows CE is designed,

including "Compact," Connectable,"

Compatible," "Companion," and "Efficient."

- Supports various processor x86, MIPS, SH, ARM

- Real TimeOS

- Preemptive

- Max 32 process supported on or previous version of wince

6.x

- XIP

- Small memory foot print.

- Suitable for small gadgets with like Portable media

players, Mobile phones

A device driver is a code that performs device control

operations specific to the device being addressed.

It is software layer that lies between applications and the

actual device.

or a more formal definition would be

Device drivers are distinct black boxes that make a

particular piece of hardware respond to a well defined

internal programming interface.

only windows embedded compact 7 will support dual core

NTDS.dit is a active AD data base file stores in %

systemroot%system32NTDSntds.dit.

Edb.chk, Edb*.log, res1, res2 are the files related to AD

In Keil

void serial_ISR() interrupt 4 using 0

{

}

& in AVR studio

SIGNAL(Inteerupt_no)

{

}

hardware intterupt normally redirects the uC to predefined

addresses. In case of high end processors the interrupt

table will decide the interrupt vector address and whenever

intterrupt pin goes low, the table is searched for type and

source of interrupt.

Interrrupt Latency means the time taken by the processor to

pass the control to ISR after the interrupt is raised.

Certainly this is the hardware feature.

Footprint of the OS matters because with the same compiler

and same optimization techniques, Different OS's will have

different footprint.

So this is can be looked upon while selecting the RTOS.

RTOS can be chosen looking at various API support it

provides. Synchronization support, Scheduler algos, and

memory management of the OS.

When low priority thread is service and high priority theas

is keep on waiting.This situation is called priority

inversion.because even though thread have high priority it

is not executed.

solution:There are different solution one of them is

priority inheritance,It means change the priority of the

thread.make high priority thread to low and lower priority

thread to high.

In this way only the rule high priority should execute first

is follow.

"IRQ is serviced at a normal priority level and FIQ is

serviced at high priority level." This statement is wrong

FIQ is the fast interrupt i.e. the latency time taken is less because in the FIQ mode (in case of ARM architecture where these modes are encountered) the mode has an additional set of 8 general purpose registers which means in case of the banked registers there is no need to store these registers into stack when the interrupt occurs.

That means r0 to r7 only needs to be stored while moving from User mode to FIQ mode whereas while moving from to IRQ mode r0 to r12 needs to be stored.

Top down methodology is one where overall picture of the

system is defined first. Then we go into the details of the

sub-systems in the next level and so on. So to brief this,

first the complex system is seen as a whole and then this

is broken down to smaller simpler pieces.

Top down approach is preferred when understanding of the

complete system is done. Sufficient knowledge of the system

is required.