Embedded Systems Interview Preparation Guide

Fifo(First In Last Out) is a memory sturcture where datas can be stored and retrived (in the order of its entery only). This is a queue,wheras Memory is a storage device which can hold datas dynamically or at any desired locations and can be retrived in any order.

"Normally you are at liberty to give functions whatever
names you like, but ``main'' is special - your program
begins executing at the beginning of main. This means that
every program must have a main somewhere." Kernighan &
Ritchie - The C Programming Language 2ed. p.6

%program for FIR filters

disp('choose the window from the list');
ch=menu('types of
windows','bartlett','blackman','hamming','hanning','kaiser',
'rectangular');
rp=input('enter the passband ripple in db');
rs=input('enter the stopband ripple in db');
wsample=input('enter sampling frequency in hertz');
wp=input('enter the passband frequency in hertz');
ws=input('enter the stopband frequency in hertz');
wp=2*wp/wsample; ws=2*ws/wsample;
p=20*log10(sqrt(rp*rs))-13;
q=14.6*(ws-wp)/wsample;
N=1+floor(p/q);
N1=N;
if(rem(N,2)==0)
N1=N+1;
else
N=N-1;
end
switch ch
case 1
y=bartlett(N1);
case 2
y=blackman(N1);
case 3
y=hamming(N1);
case 4
y=hanning(N1);
case 5
beta=input('enter beta for kaiser window');
y=kaiser(N1,beta);
case 6
y=boxcar(N1);
otherwise
disp('enter proper window number');
end
disp('select the type of filter from the list');
type=menu('types of
filters','lowpass','highpass','bandpass','bandstop');
switch type
case 1
b=fir1(N,wp,'low',y);
case 2
b=fir1(N,wp,'high',y);
case 3
b=fir1(N,[wp ws],'bandpass',y);
case 4
b=fir1(N,[wp ws],'stop',y);
otherwise
disp('enter type number properly');
end
[h,w]=freqz(b,1,512);
magn=20*log10(abs(h));
phase=(180/pi)*unwrap(angle(h));
w=(w*wsample)/(2*pi);
subplot(2,1,1); plot(w,magn),grid on;title('magnitude
plot'); subplot(2,1,2); plot(w,phase),grid on;title('phase
plot');

Before reading the data if you are giving the stop bit then
the communication is stopped.so after sending the data you
will give the stop bit.

Anti aliasing filter reduces errors due to aliasing. If a
signal is sampled at 8 kS/S, the max frequency of the input
should be 4 kHz. Otherwise, aliasing errors will result.
Typically a 3.4kHz will have an image of 4.6 khz, and one
uses a sharp cut off filter with gain of about 1 at 3.4kHz
and gain of about 0.01 at 4.6 kHz to effectively guard
against aliasing. Thus one does not quite choose max
frequency as simply fs/2 where fs is sampling frequency.
One has to have a guard band of about 10% of this fmax, and
chooses max signal frequency as 0.9*fs/2

A fourth order Butterworth filter can be made as cascade of
two seond order LP filters with zeta of 0.924 and 0.383.
One can use a bilinear transformation approach for
realising second order LP filters. Using this technique
described well in many texts, one can make two second order
LP filters and cascade them.

its not a embedded system...bcoz it will be a part of a
embedded system and it does not work on any software..

In the x86 processor architecture, memory addresses are
specified in two parts called the segment and the offset.
One usually thinks of the segment as specifying the
beginning of a block of memory allocated by the system and
the offset as an index into it. Segment values are stored
in the segment registers. There are four or more segment
registers: CS contains the segment of the current
instruction (IP is the offset), SS contains the stack
segment (SP is the offset), DS is the segment used by
default for most data operations, ES (and, in more recent
processors, FS and GS) is an extra segment register. Most
memory operations accept a segment override prefix that
allows use of a segment register other than the default
one.

Special function registers like accumulator,Program
controller(PC),data pointer(DPTR),TMOD and TCON (timing
registers),3 register banks with r0 to r7,Bit addressable
registers like B.

programming logical control system