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gviaud

Using 16Bit variables

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I would like to know how to extract the two 8bit sub-components from a 16 bit variable and put them in an 8bit variable.

 

psudocode example:

 

psudo()

{

 short X16 =  52428;

 char Lower8 = 0;

 char Upper8 = 0;

 

 Lower8 = GetLower(X16);

 Upper8 = GetUpper(X16);

}

 

Upper8 and Lower8 should now equal 204...

 

How do I make "GetLower" and "GetUpper" with available operand?

 

The reason I ask is, I am having trouble with some 16Bit code and think there may be a bug but can not debug it without being able to actually "see" what the values are...

 

Thanks,

 

George

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You can shift the bits 8 places like this.

 

  //////////////////////////////////////////////////
 // From one 16bit variable two 8bit variables
 int  Var16bit = 0xBCAC;	// 0xBCAC == 48300
 char Var8bit1;
 char Var8bit2;

//Because Var8bit1 is an 8bit variable only 0xAC is left over.
 Var8bit1 = Var16bit;    // AC == 172 
// Shift the 8 bits 8 places (0x00BC)
 Var8bit2 = Var16bit>>8; // BC == 188

 
 //////////////////////////////////////////////////
 // From two 8bit variable one 16bit variable
 Var8bit1 = 0xAC; // AC == 172
 Var8bit2 = 0xBC; // BC == 188
 Var16bit = 0;
 
 Var16bit = Var8bit2*256+Var8bit1; // 0xBCAC == 48300

Regards,

David

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Guest ysj

try these codes

this will take up less memory

 

#include

 

short X16@0x20;

char Lower8@0x20;

char Upper8@0x21;

 

main()

{

char UpperX16, LowerX16;

 

for (;:)

{

X16 = 52428;

LowerX16 = Lower8;

UpperX16 = Upper8;

 

X16 = 0xa3b4;

LowerX16 = Lower8;

UpperX16 = Upper8;

}

}

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Guest Pavel

Here is another solution from similar topic from the old forum:

 

I just create a global variable and access it using assembly like this:

int Value;
char bHi;

asm movf _Value+1, W
asm movwf _bHi

 

Now the high bite of Value is in bHi. I make these variables global because it makes it easier to name them since the name is just the variable name with an underscore.

 

Regards,

Pavel

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