hi all Help me out

Good thing there is only one type of embedded processor. Wait there are 100's What CPU, what language?

Checking bits in usually done by masking. logical ANDs and ORs

Seperating byte C asm ? Shift and mask, pointers, arrays, unions.

Can you see what the following code does?

...

unsigned int a = 0x10000B00; unsigned int mask = 0x00000001; unsigned char bit_check = 8;

if (a & (mask hi everybody..

well the processor is ARM 7 core based processor. i am using c for coding. well i want to connect the processor with the keyboard using the RS232 protocol. as the keyboard i am using is not a normal key board it is pocket keyboard CE-KB1 (usually used with Zaurus pocket (MI-110M)) after the receiving of data(i.e keycode) the flag bits in the UART get changed i used the "Shift and mask" technique as per your advice its working Thanks for ur help..

Tahnk you very much

Neil wrote:

I normally use a bit mask such as if you want to look at bit 2 (0100b or 4h) then bitwise AND the flag register with the bit's number - i.e if (FlagRegister & 0x04) {. Since you are working with a UART remember that doing this on the data register counts as a read and will (normally) pop the value off the top of a FIFO, if you are using one.

Which microcontroller is this specifically - you mentioned it was ARM7? I think you'll probably find that only the lower eight bits of the 32bit word contain recieved data. If the UART is anything like the Sharp one I've worked with (and some others) then bits 8, 9, 10 and 11 will contain error flags too.

So, to (possibly) answer both your questions I would try something like:

unsigned char RxCharacter; unsigned int DataWord;

// Pointers to UART registers - likely to be different on your system. unsigned int *DataReg = 0xFFFC0000; //Pointer to data register. unsigned int *FlagRegister = 0xFFFC0018; // pointer to flag register

while ((*FlagRegister & 0x10)); // loop until bit 4 of the flag register gets cleared. // On my uart this means something has been received. Potentially infinite loops // are BAD though so find a better way - this is just an example.

DataWord = *DataReg; // Read the data register (may pop a FIFO)

if (DataWord & 0x0F00) { // check if any of the error bits are set - if the UART supports this return ERROR; // quit if they are } else { // otherwise store the data RxCharacter = (unsigned char)DataWord; // use a cast to strip off the top 24 bits. }

This will work on a Sharp 79524 ARM7 but your device may be similar.

I am not understanding the source of your confusion. The above code fragment does exactly what it says - it checks to see if the n'th bit as specified in the bit_check variable (where the LSB would be labelled as bit 0) is set or clear.

Or are you been confused by the "(mask

And I can't understand who didn't understand the code... The original author of this thread has understood the thing I wanted to say.

My sole purpose was to show a real code segment that uses ANDing and ORing for checking the bit status and I think I succeeded in that.

--Himanshu

Sim> >> Can you see what the following code does?

Sorry, I misunderstood your reason behind posting - I thought that _you_ were asking how the code fragment worked. :-)

Simon.

Ha! I was also confused to know why I am confused for the confusing code that I wrote to confuse others... PJ? I know...

--Himanshu

Sim> >> And I can't understand who didn't understand the code...