User manual

228
mikoC PRO for PIC32
MikroElektronika
Here is an example of using asm instructions:
unsigned myvar absolute 0x2678;
unsigned long myvar1;
const char msg[] = “Test” absolute 0x3652;
void main() org 0x11234 {
myvar = 5;
myvar1 = 0xABCDEFAB;
asm {
MOV _myvar, w0 ; move myvar to W0
nop
MOV #6, W0 ; move literal 6 to W0
MOV W0, _myvar ; move contents of W0 to myvar
MOV #lo_addr(_myvar), W1 ; retrieve low address word of _myvar and move
it to W1 (0x2678 -> W1)
MOV #hi_addr(_myvar), W1 ; retrieve high address word of _myvar and move
it to W1 (0x0000 -> W1)
MOV #lo_addr(___main_Label1), W0 ; retrieve lo address word of Label1 and move
it W0 ( PC(Label1) ) -> W0
MOV #hi_addr(_main), W0 ; retrieve hi address byte of main routine and
move it to W0 (0x0001 -> W1)
MOV #lo_addr(_msg2), W0 ; retrieve low address word of constant msg
and move it to W0 (0x3652 -> W1)
MOV _myvar1+2, W1 ; accessing hi word of myvar1 variable and
move it to W1 (0xABCD -> W1)
}
Label1:
asm MOV #hi_addr(___main_Label1), W0 // retrieve hi address word of Label1 and move
it W0 (PC(Label1)) -> W0
goto Label1;
}
When using asm instructions that expect parameters like lit1, lit4, slit6, slit6, bit4, etc. be sure to preceed
them with the ‘#’ (hash symbol) to ensure proper functioning.
Example:
BSET f, #5 ; set bit #5 in f register
MOV #16000, Wnd ; move number #16000 to destination working register
ADD Ws, #-5, Acc ; add number #-5 to accumulator
Asm code and SSA optimization
If asm code is mixed with the C code, keep in mind that the generated code can substantially differ when SSA optimization
option is enabled or disabled.
This is due to the fact that SSA optimization uses certain working registers to store routine parameters (W10-W13),
rather than storing them onto the function frame.
Because of this, user must be very careful when writing asm code as existing values in the working registers used by
SSA optimization can be overwritten.
To avoid this, it is recommended that user includes desired asm code in a separate routine.