8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes : Forum / topic http://www.8051projects.net/ Learn to make simple microcontroller projects, pic, 8051, avr and arm projects. download 8051 projects, tutorials, libraries, sample codes. join the microcontroller discussion forum and ask doubts regarding electronics. the best source for 8051 over internet. en-gb 2008 Rickey's World contact@nospam.com (Ajay Bhargav) contact@nospam.com (Ajay Bhargav) Wed, 07 Jan 2009 13:36:42 -0800 Wed, 07 Jan 2009 13:36:42 -0800 http://backend.userland.com/rss e107 (http://e107.org) 60 Search Search 8051 Microcontroller Projects AVR PIC Projects Tutorials Ebooks Libraries codes query http://www.8051projects.net/search.php doubts http://www.8051projects.net/forum-t11744.html > and << do in C programming ??]]> Fri, 15 Aug 2008 06:12:27 -0700 http://www.8051projects.net/forum-t11744.html Re: doubts http://www.8051projects.net/forum-t11744.html contact@nospam.com (Ajay Bhargav) Fri, 15 Aug 2008 10:14:15 -0700 http://www.8051projects.net/forum-t11744.html Re: doubts http://www.8051projects.net/forum-t11744.html ۞ TPS ۞ wrote ...

less then greater than



Are you sure that it is greater or less than?? According to my textbook. >> means shift right and << shift left. But i don know where to apply both of them and how are are used...]]> contact@nospam.com (Ajay Bhargav) Sat, 16 Aug 2008 04:13:38 -0700 http://www.8051projects.net/forum-t11744.html Re: doubts http://www.8051projects.net/forum-t11744.html u are right. these are indeed left/right shift operators. The most general use of these operators in our embedded c programming is to set/clear an individual bit of a single byte.
the left shift operator << is used in this case.
suppose u want to set the 'n' th bit of a register say reg1. then u can write the following instruction:
reg1 |=(1<<n);
similarly if u want to reset/clear a bit of the register u can use the instruction:
reg1 &=~(1<<n);
this logic is extensively used in AVR programming as AVRs have only byte level operations unlike 8051 which supports bit level manipulations .
the AVR library also included a macro _BV(n) which is equivalent to (1<<n) for this very reason.

]]> contact@nospam.com (Ajay Bhargav) Sat, 16 Aug 2008 06:37:19 -0700 http://www.8051projects.net/forum-t11744.html Re: doubts http://www.8051projects.net/forum-t11744.html
x>>1
means the value of x be shifted one times towards right
like in
0000 0010 >>1 will give 0000 0001
similarly,


x<<1
means the value of x be shifted one times towards left
like in
0000 0010 <<1 will give 0000 0100


in some micro controllers bit addressing is not provided (ex. lpc2138)
there the whole (8 bit /32 bit) register needs to be read or written to.
in such a case you will need these (<<,>>) operators also known as bitwise shift operators.

ex. writing 1 to 5 bit of resister A
A = 0x01 << 5 ;
that will make A= 0010 0000 = 0x20
similarly if you want to read the status of the 5th bit of A register
(A>>5)&&(0x01) = result;

if the fifth bit is one u get result as 1
if not the result will be a zero..

hope that will make there use clearer!
]]> contact@nospam.com (Ajay Bhargav) Sat, 16 Aug 2008 22:10:28 -0700 http://www.8051projects.net/forum-t11744.html