how can i access to every bit of ADRESH

[Jiadong Yao]

Using the ADC
I want to display the result on RB0 to RB5 and RA2 to RA3.

How can i get every single bit in the ADRESH register then assign them to every port?

Thanks

 

[milan.rajik]

Which Compiler are you using ?

 

[Jiadong Yao]

Which Compiler are you using ?

Hi, i am using XC8 compiler.

 

[milan.rajik]

Is your ADC result right justified or left justified ? If right justified then ADRESH only contains 2 bits (lower 2 bits of ADRESH) of data, other higher bits are cleared. Did you mean to say ADRES that is ADRESH and ADRESL ?

See if this works.

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Code C - [expand]
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LATB = (LATB & 0xC0) | (ADRESH & 0x3F)
LATAbits.LATA2 = ((ADREH & 0x40) >> 6)
LATAbits.LATA3 = ((ADREH & 0x80) >> 7)

---

 

[betwixt]

note in post #4, ADREH should read ADRESH !

Brian.

 

[Surender Reddy]

better to go for right shift bitwise operators with registers.......

 

[Jiadong Yao]

Is your ADC result right justified or left justified ? If right justified then ADRESH only contains 2 bits (lower 2 bits of ADRESH) of data, other higher bits are cleared. Did you mean to say ADRES that is ADRESH and ADRESL ?

See if this works.

---

Code C - [expand]
1
2
3
LATB = (LATB & 0xC0) | (ADRESH & 0x3F)
LATAbits.LATA2 = ((ADREH & 0x40) >> 6)
LATAbits.LATA3 = ((ADREH & 0x80) >> 7)

---

Hi, nice to see you.
Well actually i dont understand your code. could you explain me what "|" and ">>" mean?
why you use LAT rather than PORT? is there any difference?? i am always confused about these two.

thank you

 

[milan.rajik]

| means ORing and >> means right shift the bits. If you use PIC18F then you have to use LATx for output port.

 

[Jiadong Yao]

| means ORing and >> means right shift the bits. If you use PIC18F then you have to use LATx for output port.

But i always write code in this way: e.g. PORTB = ADRESH;
Then the 8 bits will be shown on all RBs.
isn't it correct?

by the way, can i add you on facebook? if you don't mind, you can add me. my name is jiadong yao.

 

[milan.rajik]

Yes, if you are assigning 8 bits of ADRESH to 8 bits of PORTB then it is correct but if you are using 18F devices then use LATB.

 

[Jiadong Yao]

Yes, if you are assigning 8 bits of ADRESH to 8 bits of PORTB then it is correct but if you are using 18F devices then use LATB.

I am using 18F device. but when i assign, i still use PORTB rather than LAT. it seems that everything works fine.
what is the problem?? i really dont know.

 

[betwixt]

In most cases both will work. PORTx is the same as on other PIC families, the LAT (LATch) instruction writes to a latched output pin and avoids the potential 'read modify write' problem. As LAT is always safe to use, it is the preferred method.

Brian.

 

[Jiadong Yao]

In most cases both will work. PORTx is the same as on other PIC families, the LAT (LATch) instruction writes to a latched output pin and avoids the potential 'read modify write' problem. As LAT is always safe to use, it is the preferred method.

Brian.

I google the "read modify write" problem.
Now i completely understand. Thank you very much.