Simple PIC programming problem - Electronic Circuits Projects Diagrams Free

c36041254 · 13th May 2008, 08:06 AM

I have successfuly programmed LED flashing programme with those normal codes (MOV and all that..) now, I'm trying this XOR one but, don't understand why this is not working.

Code:

list p=16f690
	#include<p16f690.inc>
	
	#define LED PORTC,0;Define pin 0 of port c as LED
	
	__CONFIG  _MCLRE_ON & _CP_OFF & _WDT_OFF & _INTRC_OSC_NOCLKOUT
	ERRORLEVEL    -302

TEMP_VAR UDATA
temp     RES 1
delay1   RES 1;reserves 1 byte for delay1
delay2   RES 1;reserves 1 byte for delay2

;*******************************************************************
Main:;Main programme begains
	CODE 0x05; Start address at 0x05
Setpins:; Select output and input
	bsf STATUS,RP0 ;Switch to bank 1
	movlw b'11110';MOVe 11110 to W
	movwf TRISC    ;set pin 0 of PORT C as output
	bcf STATUS,RP0 ;Switch back to bank 0
	movlw b'00001';MOVe 00001 to W
Start:
	xorwf LED
	call Loop
	call Loop
	goto Start
Loop:
	decfsz delay1,1
	goto Loop
	decfsz delay2,1
	goto Loop
	return
	END

**Nigel Goodwin** · 13th May 2008, 08:18 AM

How about specifing a destination for the XORWF instruction?.

ericgibbs · 13th May 2008, 08:18 AM

hi,
I cannot see that LED has been declared.?

xorwf LED

You pipped me again Nigel, I must be getting slower...

I'll opt out of this one.

Gayan Soyza · 13th May 2008, 08:29 AM

Code:

Start	movlw 	b'00001'
	xorwf	PORTC,F
	call 	Loop
	call 	Loop
	goto 	Start

c36041254 · 13th May 2008, 09:35 AM

I tried what Gayan Soyza suggested but, that is not working and I am already using Nigel's tutorials they are very helpful but, I can't see any special help on XOR, please help me, I'm on this for hours, trying to blink just an LED with XOR code !, please point out where is the mistake I'm just a layman!

geko · 13th May 2008, 09:53 AM

At the top of your code you use the following

Code:

#define LED PORTC,0;Define pin 0 of port c as LED

but then you try to toggle the LED using this instruction in the main code

Code:

xorwf LED

which if you substitute your definition for 'LED' is

Code:

xorwf PORTC,0

The 0 here isn't the bit you want to toggle it's the destination for the result of the XOR operation. The 0 tells it to put the result in W so your code never writes anything back to PORTC.

What you want is

Code:

 
xorwf PORTC, F

geko · 13th May 2008, 10:27 AM

Also, you need to turn off analogue mode and set the port to digital I/O. See datasheet

Code:

 
Setpins:; Select output and input
 
      bsf STATUS,RP0               ;Switch to bank 1
      movlw b'11110'                 ;MOVe 11110 to W
      movwf TRISC                   ;set pin 0 of PORT C as output
 
      bcf   STATUS, RP0           ; Switch to bank 2   
      bsf   STATUS, RP1
 
      bcf   ANSEL, ANS4           ; Set PORTC, 0 to digital mode
 
      bcf STATUS,RP0              ;Switch back to bank 0
      bcf STATUS,RP1
 
     movlw b'00001'          ;MOVe 00001 to W
Start:        
 
     xorwf PORTC,F
     call Loop
     call Loop
     goto Start
Loop:         
 
     decfsz delay1,1
     goto Loop
     decfsz delay2,1
     goto Loop
     return

c36041254 · 13th May 2008, 11:47 AM

Hmm....... that works

, but what I did'nt understand is that why it is:

bcf ANSEL,ANS4

and why not,:

bcf ANSEL,ANS0

After all the LED is connected at pin 0 of port c and not at pin 4

I mean the data sheet says :

Setting the ANSx bit of a corresponding pin will
cause all digital reads of that pin to return ‘0’ and also
permit analog functions of that pin to operate correctly.
Please explain as easily as possible, Thank you for your help !!

geko · 13th May 2008, 11:55 AM

Quote:

Originally Posted by c36041254

Hmm....... that works

, but what I did'nt understand is that why it is:

bcf ANSEL,ANS4

and why not,:

bcf ANSEL,ANS0

After all the LED is connected at pin 0 of port c and not at pin 4

Read the data sheet again. The Analogue bit numbers don't correspond to the same port bit numbers; how could they since you have PortA,0 and PortC,0 and they're both analogue inputs.

c36041254 · 13th May 2008, 01:28 PM

I'm sorry but I still don't get that, I know this may sound stupid to you but I'm working with .ASM since last few days only, I have checked all registers associated with port c (that is given in table format in datasheet) and I found that ANS4 is corresponds to bit 4 and bit 4 also corresponds to pin 4 of port c, I know you are trying to tell me something quite different but, if you can make it more simpler than I'll be very grateful !

geko · 13th May 2008, 02:13 PM

Quote:

Originally Posted by c36041254

I'm sorry but I still don't get that, I know this may sound stupid to you but I'm working with .ASM since last few days only, I have checked all registers associated with port c (that is given in table format in datasheet) and I found that ANS4 is corresponds to bit 4 and bit 4 also corresponds to pin 4 of port c, I know you are trying to tell me something quite different but, if you can make it more simpler than I'll be very grateful !

See Figure 9-1 (Page 107) in the 16F690 datasheet (http://ww1.microchip.com/downloads/e...Doc/41262E.pdf)
Also Table 9-2 (page 118)
And section 4.2.1 (page 60)

If you want a port bit to function as digital I/O you have to clear the corresponding bit in the ANSEL or ANSELH registers.

AN0 thru AN7 are set in the ANSEL register and AN8 thru AN11 in ANSELH.

If for example you want to use port RB4 as digital I/O you would clear ANS10 bit in ANSELH register.

c36041254 · 13th May 2008, 03:01 PM

Oh!

that was very easy, right before my eyes, it is also given in table 1.5, Thank you very much and sorry to bother you about this, now I think that it is out of quastion that why Microchip built it like this (AN4 fo RC0) as it is related to archtructure stuff, is'nt it ?, we just have to accept as it is.

blueroomelectronics · 13th May 2008, 03:13 PM

To save memory they pack lots of sometimes unrelated bits into a single register.

13th May 2008, 08:18 AM	(permalink)
Nigel Goodwin Super Moderator	How about specifing a destination for the XORWF instruction?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

13th May 2008, 08:18 AM	(permalink)
ericgibbs Experienced Member	hi, I cannot see that LED has been declared.? xorwf LED You pipped me again Nigel, I must be getting slower... I'll opt out of this one. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

13th May 2008, 08:29 AM	(permalink)
Gayan Soyza Experienced Member Blog Entries: 1	Code: Start movlw b'00001' xorwf PORTC,F call Loop call Loop goto Start __________________ Gayan Forum Supporter

13th May 2008, 09:35 AM	(permalink)
c36041254 Experienced Member	Re:Simple PIC pro. problem I tried what Gayan Soyza suggested but, that is not working and I am already using Nigel's tutorials they are very helpful but, I can't see any special help on XOR, please help me, I'm on this for hours, trying to blink just an LED with XOR code !, please point out where is the mistake I'm just a layman!

13th May 2008, 09:53 AM	(permalink)
geko Experienced Member	At the top of your code you use the following Code: #define LED PORTC,0;Define pin 0 of port c as LED but then you try to toggle the LED using this instruction in the main code Code: xorwf LED which if you substitute your definition for 'LED' is Code: xorwf PORTC,0 The 0 here isn't the bit you want to toggle it's the destination for the result of the XOR operation. The 0 tells it to put the result in W so your code never writes anything back to PORTC. What you want is Code: xorwf PORTC, F __________________ Pete picprojects.org.uk

13th May 2008, 11:47 AM	(permalink)
c36041254 Experienced Member	Re:Simple PIC pro. problem Hmm....... that works , but what I did'nt understand is that why it is: bcf ANSEL,ANS4 and why not,: bcf ANSEL,ANS0 After all the LED is connected at pin 0 of port c and not at pin 4 I mean the data sheet says : Setting the ANSx bit of a corresponding pin will cause all digital reads of that pin to return ‘0’ and also permit analog functions of that pin to operate correctly. Please explain as easily as possible, Thank you for your help !!

13th May 2008, 01:28 PM	(permalink)
c36041254 Experienced Member	Re:Simple PIC pro. problem I'm sorry but I still don't get that, I know this may sound stupid to you but I'm working with .ASM since last few days only, I have checked all registers associated with port c (that is given in table format in datasheet) and I found that ANS4 is corresponds to bit 4 and bit 4 also corresponds to pin 4 of port c, I know you are trying to tell me something quite different but, if you can make it more simpler than I'll be very grateful !

13th May 2008, 03:01 PM	(permalink)
c36041254 Experienced Member	Re:Simple PIC pro. problem Oh! that was very easy, right before my eyes, it is also given in table 1.5, Thank you very much and sorry to bother you about this, now I think that it is out of quastion that why Microchip built it like this (AN4 fo RC0) as it is related to archtructure stuff, is'nt it ?, we just have to accept as it is.

13th May 2008, 03:13 PM	(permalink)
blueroomelectronics Experienced Member Blog Entries: 4	To save memory they pack lots of sometimes unrelated bits into a single register. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

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