I am using the PIC18F4320. I am writing in C-language and using MPLAB
C18 tool suite(compiler V2.2). I have a question about the ADC result
registers (ADRESL and ADRESH). I must use all 10 bits; therefore, I have
to do the simple task of taking the two 8-bit result registers and
combining them into a 16-bit integer. The following code is how I did
it:

(obviously before this I set the ADC result to be right justified and
VBattNew is defined as an unsigned int)

(I also send the raw values out the USART before the statements below -
getting exactly what one would expect in each of the bytes)

//Sent data out USART here
VBattNew =3D ADRESL;		// Get low byte
//Sent data out USART here
VBattNew |=3D (ADRESH << 8);	// Combine with the high byte into 16
int
//Sent data out USART here


The problem is the high byte continually gets cleared to 0x00 - I cannot
get past 255 decimal.

I even sent the raw data out the USART before, between and after for
inspection, and it is clear the left shift and integer assignment is
clearing the high byte?

 I tried the code below to make sure I was not trying to do much at once
with the above syntax - same problem:

//	VBattNew =3D ADRESL;			// Get low byte
//	temp =3D ADRESH;
//	temp << 8;
//	VBattNew =3D temp | VBattNew;

The final fix which works is using the ADRES definition in the
p18f4320.h file - which apparently is the entire 16-bit concatenation of
the two bytes; as follows:

VBattNew =3D ADRES;	// This works

But, I want to understand why my code did not work - I bet it is
surprisingly simple (as always - its one bit screwing things up). By the
way I did search the archives and found someone posted code the same way
I did it - should be a slam dunk.

Thanks for your time guys,
Shawn

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