Avr bitwise operators in c
I have to check initial bit condition before making bitwise operation before shitfing any a bit to location? I hope it's making more sense… Though you'd better lookup for a course on combinatory logics, which is the basic to perfectly handle when doing embedded programming.
Microcontroller Bitwise Operators + #1 - Tutorial #8
The compiler will convert it to a number before the processor sees it, so the processor doesn't perform the shift. But the cost for efficiency for a one time assignment is vastly less than the cost to maintain the source code.
I'm not sure what you are doing with the arithmetic in your question. The statement takes the original contents of DDRC and ors it with something like 0b where the 1 is in the DDRC0 position , and assigns it back to DDRC. There are more efficient ways of setting a bit and clearing a bit on many microcontrollers that does not involve the other bits, ie you don't have to use OR and AND to maintain the other bits.
There are AVR machine instructions to set a bit and clear a bit of a register, namely "SBR" and "CBR". Also see "CBI" and "SBI" if you need to set an IO register.
I'm not sure if the AVR compiler is smart enough to convert C-style operations which operate on bytes into individual bit statements. But usually there are intrinsics to do this. I'm not an AVR user. Perhaps you can use gcc asm to insert SBR and CBR. But I wouldn't bother with this unless you need to save a cycle in an ISR. It's not worth the headache.
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Log In Sign Up. Join the Stack Overflow Community. Stack Overflow is a community of 7. Join them; it only takes a minute: AVR bitwise C operations Ask Question. I have a question about ATMEGAP programing in Atmel Studio 6. Isn't it faster to assign a binary to register than making shift operation? If I understand correctly, but please correct this!! Lee Taylor 4, 7 21 Dovydas 37 1 6. This question is very unclear.
Have you looked at the machine code that your C code generates and determined that it is suboptimal? AtmegaP, AVR-GCC compiler from atmel studio. If i'am not mistaken. Question is about bitwise operations, on 8bit registers. What is better to get there walues and make bitwise opperations to change them or to change once according to needs?
bit manipulation - Bitwise operations, assembly - Stack Overflow
About operations, please have a look at truth tables: Now to answer your question: Consider the following made up register FOO: Ok, thanks, don't be mad! I was confused that it shits initial register, not creating new variable to or xor and or anything to make operation and return value to register. Very vell explaned and commented, Thanks again. No, it is slower. UncleO 7, 2 14 So there i have a question is there a safe bitwise operator to change only one bit to 1 from 0 or from 0 to 1 if i don't know other values.
Sorry I have a litle knowledge in bitwise opperations.
AVR Bitwise Operations in C – irexapezoren.web.fc2.com
Thanks for supporting and deep explanation. So if i shift to much i will shift out other valiables? The shift operator is acting on the constant 1. There are no variables being shifted. Ok, can you edit post so even i could understand.. Sign up or log in StackExchange.
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