Porting code from PIC16F877 to PIC18F4520: Key instruction and register changes?

good afternoon
gentlemen
I need to migrate from 16f877 to 18F4520 18F4520 but does not have the same instructions that 16f made ​​some changes based on the datsheet 18f but not working without going straight to the sensor response, I need to know if these changes I've made are correct if not 're correct me by favor.os points concerned the program are marked with a question.

sbit at RA0_bit Date ;
sbit at DataDir TRISA0_bit ;
message1 char [ ] = "Temp = 00.0 C " ;
message2 char [ ] = "RH = 00.0 % ;"
unsigned short TOUT = 0 , CheckSum , i ;
unsigned short T_Byte1 , T_Byte2 , RH_Byte1 , RH_Byte2 ;
StartSignal void ( ) {
DataDir = 0 / / Data port is output
Data = 0 ;
Delay_ms ( 25);
Date = 1 ;
Delay_us (30);
DataDir = 1 / / Data port is input
}
unsigned short CheckResponse ( ) {
TOUT = 0;
TMR2 = 0;
T2CON.TMR2ON = 1 / / start timer
while ( ! date && ! ​​TOUT ) ;
if ( TOUT ) return 0;
else {
TMR2 = 0;
while ( date && ! ​​TOUT ) ;
if ( TOUT ) return 0;
else {
T2CON.TMR2ON = 0;
return 1;
}
}
}
unsigned short ReadByte ( ) {
unsigned short a = 0 , t ;
DataDir = 1;
for (i = 0 : i 100 ) a | = 1 40us , Date is 1 / / I put 200 on the counter this correct?
}
return a ;
}
void interrupt () {
if ( PIR1.TMR2IF ) {
TOUT = 1;
T2CON.TMR2ON = 0 / / stop timer
PIR1.TMR2IF = 0 / / Clear TMR0 interrupt flag
}
}
void main ( ) {
unsigned short check ;
ANSEL = 0 / / Set AN pins to digital / how can I configure for PIC18F4520 with external clock 20mhz ?
ANSELH = 0 ; / how can I configure for PIC18F4520 ? with external clock 20mhz ?
C1ON_bit = 0 / / Disable comparators / how can I configure for PIC18F4520 with external clock 20mhz ?
C2ON_bit = 0 ; / how can I configure for PIC18F4520 with external clock 20mhz ? / /
these were my changes but not working is correct what I did ?
ADCON0 = 0x00 ; / / Configure AN pins to Digital
ADCON1 = 0b00001110 / / AN0 ENABLED
ADCON2 = 0b10000100 / / BUILD ALL CHANNELS , JUSTIFIED RIGHT UNLESS THE YEAR
ADCON0.ADON = 1 ;/ / Enables the convert
ADCON0.GO_NOT_DONE = 1 / / BEGIN CONVERSION
while ( ADCON0.GO_DONE ) ;/ / WAITING conversion finished
ADCON0.ADON = 0 ;/ / DISABLED THE CONVERTER
ADCON0.ADON = 1 ;/ / ENABLE THE CONVERTER
CCP1CON = 0 / / C1ON_bit = 0 / / Disable comparators
CCP2CON = 0 ;/ / C2ON_bit = 0;
end of my changes but it is not working , I made this change to migrate this correct ?
TRISB = 0;
TRISA = 0x01 , / / configure the input pins
TRISD = 0;
TRISB = 0;
TRISA = 0x01 ;
TRISD = 0, / / configure the input pins
INTCON.GIE = 1 / / Enable global interrupt
INTCON.PEIE = 1 / / Enable peripheral interrupt
/ / Configure Timer2 module
PIE1.TMR2IE = 1 / / Enable Timer2 interrupt
T2CON = 0 ; / / Prescaler 1:1 , and Timer2 is off INITIALLY
PIR1.TMR2IF = 0 / / Clear INT flag bit TMR
TMR2 = 0;
Lcd_Init ();
Lcd_Cmd ( _Lcd_Clear );
Lcd_Cmd ( _LCD_CURSOR_OFF );
do {
Delay_ms ( 1000) ;
StartSignal ();
CheckResponse check = ( ) ;
if ( ! check ) {
Lcd_Cmd ( _Lcd_Clear );
Lcd_Out ( 1, 1, " In response" );
Lcd_Out ( 2, 1, " from the sensor ");
}
else {
RH_Byte1 ReadByte = ();
RH_Byte2 ReadByte = ();
T_Byte1 ReadByte = ();
T_Byte2 ReadByte = ();
Checksum = ReadByte ();
/ / Check for error in reception Date
if (CheckSum == ((RH_Byte1 + RH_Byte2 + T_Byte1 + T_Byte2) & 0xFF))
{
message1[7] = T_Byte1/10 + 48;
message1[8] = T_Byte1%10 + 48;
message1[10] = T_Byte2/10 + 48;
message2[7] = RH_Byte1/10 + 48;
message2[8] = RH_Byte1%10 + 48;
message2[10] = RH_Byte2/10 + 48;
message1[11] = 178; // Degree symbol use 223 if Greek letter appears
Lcd_Cmd(_Lcd_Clear);
Lcd_Out(1, 1, message1);
Lcd_Out(2, 1, message2);
Lcd_Cmd ( _Lcd_Clear );
Lcd_Out ( 1, 1, message1 );
Lcd_Out ( 2, 1, message2 );
}
else {
Lcd_Cmd ( _Lcd_Clear );
Lcd_Out ( 1 , 1 , " Checksum Error ");
Lcd_Out ( 2, 1, "Trying Again ... ");
}
}
} while (1);
}
I thank the help.
Rodrigo Ravanelli Lopes