Problem with setup_adc_ports on PIC16F877A

[ciprian_briscaru]

Hi guys,

I have recently tried the CCS Demo compiler for a school project. What I want to do is to make a square wave signal from a sinusoidal signal using PIC16F877A internal comparator.
So I stared a new project, from the wizard, selected the comparator configuration I wanted, selected it's inputs as analog inputs.
The problem is that when I list the ASM code generated for setup_adc_ports(AN0_AN1_AN3) it keeps writing at 0x1F address when it should write at 0x9F where the ADCON1 register is. At 0x1F is the ADCON0 register.

.................... setup_adc_ports(AN0_AN1_AN3);
0047: BCF 1F.0
0048: BCF 1F.1
0049: BSF 1F.2
004A: BCF 1F.3

I tried then using ASM code directly, but I got the same result:

#byte ADCON1 = 0x9F

.....

.................... #asm ASIS
.................... BCF ADCON1,0
005B: BCF 1F.0
.................... BCF ADCON1,1
005C: BCF 1F.1
.................... BSF ADCON1,2
005D: BSF 1F.2
.................... BCF ADCON1,3
005E: BCF 1F.3
.................... #endasm


For me it seems either a bad configuration of my PCWHD or a problem in the compiler.

What do you think?

I use CCS PCM C Compiler, Version 4.102d, 15399
and my header:

#include <16F877A.h>
#device adc=8

#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected
#FUSES RESERVED //Used to set the reserved FUSE bits

#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

[MiniMe]

Hi,

First thing .. try to use C examples from help file. By compiling working c code you will have a opportunity to view assembly instructions file... every c command or statement and under it is assembly code... intructions.

Then compare tease 2 assembly program codes.

My experience tells that there are certain situations where the order of conf. bits or registers is important.

[ciprian_briscaru]

Hi MiniMe,

Thanks for your reply and for your interest in trying to solve my problem.
As you advised, I compiled the Simple A/D (EX_ADMM.C) example write from the CCS web page.

This is the result I got:

[ckielstra]

[PCM programmer]

If you remove the "ASIS" directive, the compiler will add the ASM code to
select the bank.

[ciprian_briscaru]

Thank you for your clarifying answer. Eveything makes sense now.