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How to read a specific bit of a register?

 
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chingB



Joined: 29 Dec 2003
Posts: 81

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How to read a specific bit of a register?
PostPosted: Mon Feb 02, 2004 5:50 pm     Reply with quote
Hi,

How can I be able to read a specific bit of a register? I want to know if it is a 1 or 0?

Like the case of LVDCON register were the bit IRVST can't be set but it can be read?

Need your help? thanx
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Feb 02, 2004 6:16 pm     Reply with quote
Use a #bit statement to define the bit as a memory variable.
Then read it or write it, just like a variable. See how CCS
does this for the "t1_overflow" bit in the ex_freqc.c file:
http://www.cc.puv.fi/~t0101190/projekti/source/Examples/ex_freqc.c
Then check the PIC data sheet to find the address and bit number
of the LVDCON register and the IRVST bit, and do it the same way.
Darren Rook



Joined: 06 Sep 2003
Posts: 287
Location: Milwaukee, WI

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Re: How to read a specific bit of a register?
PostPosted: Mon Feb 02, 2004 6:17 pm     Reply with quote
chingB wrote:
Hi,

How can I be able to read a specific bit of a register? I want to know if it is a 1 or 0?

Like the case of LVDCON register were the bit IRVST can't be set but it can be read?

Need your help? thanx


How to test file 0x10, bit 1:

bit_test(*0x10,1)

This function will return TRUE (1) or FALSE (0) depending on the bit.

EDIT: PCM's method is good too. He beat me to the reply. Surprised
h
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PostPosted: Tue Feb 03, 2004 5:34 am     Reply with quote
which method requires less memory?
Neutone



Joined: 08 Sep 2003
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PostPosted: Tue Feb 03, 2004 8:01 am     Reply with quote
h wrote:
which method requires less memory?


Try both and look them over in the list file to see if they are different. Sometimes changing syntax reduces code size.
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Tue Feb 03, 2004 8:32 am     Reply with quote
Usually the same amount of memory.
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