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the pseudo opcode CLRF

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asmboy

Joined: 20 Nov 2007
Posts: 2128
Location: albany ny

the pseudo opcode CLRF

Posted: Wed Apr 22, 2009 4:52 pm

I notice that when I initialize

Code:

unsigned int16 adccon[4]={0,0,0,0};

that it generates very efficient code with
with a string of

Code:

CLRF 3F pseudo op instrux
CLRF 40
CLRF 41
CLRF 42
etc etc

however RE initing the array with a loop or whatever is very awkward
and code hoggy

since the 4.08x compiler (#ASM directive)
wont accept the pseudo op CLRF
I've been re initializing with code like this

Code:

#ASM
movlw 0
movwf 0x3F
etc and so on - matching the original static zeroing out code
#ENDASM

I know what i have to track and be careful of - in regard not getting compiler stung ( i think )

BUT is there better way to let the compiler do the reinit
like it did when i declared the vars ?

I have a number of small arrays, of different sizes - that i want to reinit together and i find that looping to do it,
sucks code space horribly- and the above ASM hack appears to do it with minimum clocks

I'd be grateful if there is a better way to let the compiler do it - but still achieve decent efficiency.

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Wed Apr 22, 2009 5:25 pm

Both the methods shown below generate CLRF statements in the .LST file.
The first one is better since it's in C.

Code:

#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

//======================================
void main()
{
int8 array[5];

array[0] = 0;
array[1] = 0;
array[2] = 0;
array[3] = 0;
array[4] = 0;

#asm
CLRF array[0]
CLRF array[1]
CLRF array[2]
CLRF array[3]
CLRF array[4]
#endasm

while(1);
}

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