Functional incompatibilities

AN3348

6/10

Doc ID 018510 Rev 2

that was given to the function by the old tools and it won't work with the new ones.

Therefore, in normal cases users should avoid writing such a code and should change it to

specific inline assembly instructions.

3.2.2

C-inline assembly interaction

The user mustn't make any kind of assumptions regarding issues as register allocation,

variable storage location and code location.

All the interaction between the C and inline assembly should be done symbolically.

The following code example is a sure way to get into troubles:

tmp = accel_tbl[tmp];

#asm( alu a = d;

ram p <- start_period. )

Here the user assumed (based on old tools behavior) that tmp would reside in register d.

This code can be easily fixed to

asm{move a,tmp@Rn; ldm p,start_period};

For more details regarding inline assembly usage please look at the Inline Assembly

chapter in eTPU_Build_Tools_Reference.pdf.

3.2.3

Inline assembly functions

Many users have written functions which are fully implemented using inline assembly.

A few changes might be needed for these functions.

Let's take as an example this code sample and see how we change it into a standard and

safe code:

/*

fract24 mc_ctrl_pid( fract24 error,

mc_ctrl_pid_t *p_pid)

*/

#asm

MC_CTRL_PID:

/* Inputs:

*/

/* register a ...... error */

/* register diob ... p_pid */

/* Limit error to range <MIN24, MAX24>

*/

if V == 0 then goto MC_CTRL_PID_I, flush.

if N == 0 then goto MC_CTRL_PID_I, no_flush.

…

#endasm

1.

All inline assembly code should reside inside a function, so first we should uncomment

the function's prototype. We should also make sure that the function's name is the

name which is used in order to call this function. Notice that in many cases users used

to call a label at the beginning of the inline assembly but since label names are local

this won't work so now we'll have to call our function with the same name of this label.

The label itself might be redundant now if it is not referenced from within the function so

we can remove or comment it:

fract24 MC_CTRL_PID( fract24 error,

mc_ctrl_pid_t *p_pid)

{

#asm