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I use KeilC uVision4 for 89C51 MCU. I use "Inline ASM Code", like this :
void main() { #pragma ASM MOV R7, #(80000/40000) #pragma ENDASM }
-> When COMPILE, ASM result file give a wrong value to R7
MOV R7, #0x00
But when i change like this :
void main() { #pragma ASM MOV R7, #(60000/30000) #pragma ENDASM }
-> The COMPILER give correct value to R7
MOV R7, #0x02
=> Seem, there must be a restriction when the ASM Compiler calculate (80000/40000) ? => And is there any way to pass this restriction. Please help me ! Regards !
In my opinion, this would be a perfect place to use a little assembly module.
"A little ASM Module", did you mean : write that Delay routines in a seperate ASM file ??? I think we have to use MACRO here ???
Yes, in an asm file.
Macros, as always, are optional.
But i don't want to use MCU to calculate vR3, vR2, vR1, let the Compiler do that, then just add the result of vR3, vR2, vR1 to the Delay() Routines.
void Delay() { #pragma ASM MOV R1, #vR1 // vR1 calculate from Compiler MOV R2, #vR2 // vR2 calculate from Compiler MOV R3, #vR3 // vR3 calculate from Compiler DJNZ R1, $ DJNZ R2, $-2 DJNZ R3, $-4 #pragma ENDASM }
I mean that, in the main routine, i call Delay MACRO :
void main() { DelayMCs(3000); // 3000 are numeric const, not variable }
then the compiler scan and compile this MACRO to something like :
#define Interval 3000 #define t3 Interval/2 #define vR3 ((t3+C2-2)/(C2+1)) #define t2 (t3+C2-(C2+1)*vR3) #define vR2 ((t2+C1-1)/(C1+1)) #define t1 (t2+C1-(C2+1)*vR2) #define vR1 ((t1+C0-0)/(C0+1)) Delay();
So vR1, vR2, vR3 is calculated from Compiler Just "Delay();" is compile to code to download to MCU
I totally agree!
That is, a separate Assembly source file; eg, delay.s
As already noted, manually hacking the registers used internally be 'C' is a Really Bad Idea!
Instructions on how to do exactly this here: www.8052.com/.../149030
Simples!
You don't have to!
"let the Compiler do that"
It will!
"then just add the result of vR3, vR2, vR1 to the Delay() Routines"
You don't need to do any of that, either!
Simply follow the instructions that I just posted...
Thanks a lot for your helps. In a couple of days, I found that the Macro should be as following :
// Delay Routine void RoutineDelayMCs(unsigned int interval) { #pragma ASM DJNZ R7, $ DJNZ R6, $-2 #pragma ENDASM } // Delay Macro -> Calculate interval to pass into Delay Routine #define MacroDelayMCs(interval) \ ((!(((interval)/2) - 257*((((interval)/2)+256-1)/257))) ? \ RoutineDelayMCs(257*((((interval)/2)+256-1)/257)) : RoutineDelayMCs(((interval)/2)+256-(((interval)/2)+256-1)/257)) // Offset Macro -> Calculate offset MCs of MOV, LCALL, RET ... command -> for better accuracy // Accuracy (if interval even, error = 0; if interval odd, error = -1 MCs // interval apply Range : 14 -> 131592 #define DelayMCs(interval) \ MacroDelayMCs(interval-10) void main() { DelayMCs(14); // This call delay 14 Machine Cycles DelayMCs(512); // This call delay 512 MCs DelayMCs(131592); // This call delay 131592 MCs }
And ... It works fine ! Of course, manually hacking the registers is really Bad. I will put the RoutineDelayMCs in an ASM Module later.
Thanks again ... all friends, Regards !