topic Re: 16 and 32 bit comnination in S12 / MagniV Microcontrollers

16 and 32 bit comnination

ernestsnaith — Mon, 14 May 2007 04:48:55 GMT

I have the timer running as well as secondary counter which increments on timer overflow. I am storing values of both at regualr intervals. Is there away of storing both 16 bit values as a long integer type to be used in expressions at a later time? Also is the reverse possible? accessing high and low parts of long int.

Cheers

Re: 16 and 32 bit combination

ernestsnaith — Mon, 14 May 2007 06:00:16 GMT

...using

Codewarrior 4.5

MC9S12XDT512

Re: 16 and 32 bit comnination

bigmac — Mon, 14 May 2007 13:04:09 GMT

Hello,

A possible method is to form a union between a long and an integer array. You can then manipulate the value of the individual words forming the long.

#define dword unsigned long

typedef union {
word wordval[2];
dword val;
} long_val;

long_val timer;

dword temp;

timer.wordval[0] = highreg;

timer.wordval[1] = lowreg;

temp = timer.val; // 32-bit value

Regards,

Mac

Re: 16 and 32 bit comnination

Obetz — Mon, 14 May 2007 14:51:12 GMT

bigmac wrote:

typedef union {
word wordval[2];
dword val;
} long_val;

long_val timer;
dword temp;

timer.wordval[0] = highreg;
timer.wordval[1] = lowreg;

I'm missing the big red warning in your suggestion. How can you be sure about the order of high and low word?

Oliver

Re: 16 and 32 bit comnination

bigmac — Mon, 14 May 2007 15:42:14 GMT

Hello Oliver,

It is my understanding that the MC9S12XDT512 is big endian, and the code was presented with this in mind. For a little endian case, the allocation of individual word values would obviously need to be reversed.

Since the problem presented was to specifically deal with hardware registers, "portability" does not seem to be an issue in this instance.

Regards,

Mac

Re: 16 and 32 bit comnination

ernestsnaith — Mon, 14 May 2007 22:10:05 GMT

Thanks