Lpc2000

Hello all, I am having some difficulty getting 10 bit resolution out 
of the A/d converter on the LPC2129.  I have an opamp directly 
coupled to the input of the A/D converter, I am running the A/d 
clock at less the 4.5 MHZ, and I am only getting 7 or 8 bits.

The code I am using is as follows:

unsigned long AtoD(void)
{   
    unsigned long  result;
    
    REG(ATOD_ADCR)=0x00000802;                          //turn the 
a/d off with the channel selected
    REG(ATOD_ADCR)=0x00200802;                          //turn the 
a/d on with the channel selected
    REG(ATOD_ADCR)=0x01200802;                          //do the a/d
    while((!REG(ATOD_ADDR))&BIT31);                     //wait for it
    green_result=(REG(ATOD_ADDR) & 0xFFFF);             //read the 
result but ignore
    REG(ATOD_ADCR)=0x01200802;                          //do the 
conversion again
    while((!REG(ATOD_ADDR))&BIT31);                     //wait for it
    result=(REG(ATOD_ADDR) & 0xFFFF);             //read the result 
(result in bits 7-16)
    result>>=6;                                   //shift result 
over so result is in lower bits
    
    return(result);               
}

I have found that if I don't cycle the power with the correct 
channel selected it doesn't change channels.  This is covered 
somewhat in the errata.  Please help!

Shane.