syntax of Shift & Rotate ?

[Don P]

I'm having little luck making the shift & rotate left & right functions work.
In particular, I declare int x[3], and set them to some arbitrary values.
Rotate_Right (as I read it) should take Rotate_Right( &x, 4 ).
First, it won't take &x. I have to specify a variable, so I try &x[0].
But my rotates don't work as expected, e.g.:

[PCM programmer]

It's correct.

I would have displayed it like this, with the MSB first:

[Wayne_]

I have to disagree with your statement PCM programmer.
If he were storing the value in a 32bit int

int32 a;
a = 0x0F000307;
rotate_right( &a, 4 ) ;

Then yes, the fact that it is a 32bit int matters. But he is using an array and manually placing the values in the correct place. Unless CCS stores array values in reverse order then his code should work

The data at x is
0x0F 0x00 0x03 0x07
00001111 00000000 00000011 00000111
Rotated right by 1
10000111 10000000 00000001 10000011
0x87 0x80 0x01 0x83

There are actually 2 bit errors so it looks like the carry bit is placed in at the wrong point.

It is unfortunate that the values being used follow what you have said PCM but the fact still remains that and array is being used not an int declaration.

Don P should check the lst file to see what it is doing!

Also you could try
rotate_right(x, 4);
Because x is an array by specifying the letter you are refering to the address of the array.

[Ttelmah]

Several other little comments.

In 'C', the name of an array _on it's own,is_ a shortcut syntax, fo the address of the array. So with x[n],

x is the address of the array
&x[0] also equals the address of the array
&x, would attempt to find the address of the address. Since the address is not actually 'stored', this is illegal.

Next comment. You declare int x[3], then are using _4_ in the second byte of the rotate instruction. This means you are going to potentially destroy the variable held in the next memory location. You have declared the array as _3_ bytes long, wih locations x[0], x[1], and x[2], then start accessing x[3].... In C, the declaration is for the size of the array (hence 3 bytes), and the indexes allowed, are zero, to the size-1. You need int x[4].
This invalid layout, is probably what is causing the behaviour to not be 'as expected'.

Best Wishes

[Wayne_]

Well spotted Ttelmah, missed the array size issue