Weird 12F629 GPIO setting? - Electronic Circuits Projects Diagrams Free

eirikr · 13th March 2004, 03:30 AM

Hi all,

I am testing the 12F629 found something very weird. The PIC is suppose to flash two LEDs on GP0 and GP1.

1. The movlw b'00001111' to set TRISIO is not a typo - bit 0 and bit 1 are supposed to be zero for output, but LEDs won't flash unless I set them to one!
:shock:
I ran the MPLAB simulator, and:
2. bsf GPIO, GP1 will set GP1 bit to zero! :?
3. bcf GPIO, GP0 will set GP0 bit to one! :roll:

Anyone has any idea what's going on?

Here is the code:

Code:

		org	0x00			
		goto	init			

init	bcf	STATUS, RP0		; Bank 0
		clrf	GPIO			; Init GPIO
		movlw	07h				; Set GP<2:0>
		movwf	CMCON			; digital IO. Turn off comparator
		movlw 	b'00001111'		; GP<1:0> output GP<3:2> inputs
  		movwf	TRISIO			; 
		bsf	STATUS, RP0		; Bank 1

main	bsf	GPIO, GP1
		bcf	GPIO, GP0
		call	delay
		bcf	GPIO, GP1
		bsf	GPIO, GP0
		call 	delay
		goto	main

delay ;;;;; delay routine ;;;;;;

**Nigel Goodwin** · 13th March 2004, 05:49 AM

Without checking the datasheet, but based on other PIC's, the bank switching looks incorrent. TRIS is usually in bank 1, and GPIO in bank 0, you have them the other way. Which is why you think setting TRIS to 1 is making them an output - it's not, it's setting GPIO high. Then in the main part of the program you're toggling the TRIS bits, switching them from inputs to outputs.

pike · 13th March 2004, 12:52 PM

yeah i just checked with the data sheet, GPIO is in bank 0, not bank 1. TRISIO is in bank 1.

eirikr · 14th March 2004, 04:08 AM

Everything works now! Thanks a lot guys!

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13th March 2004, 03:30 AM	(permalink)
eirikr	Weird 12F629 GPIO setting? Hi all, I am testing the 12F629 found something very weird. The PIC is suppose to flash two LEDs on GP0 and GP1. 1. The movlw b'00001111' to set TRISIO is not a typo - bit 0 and bit 1 are supposed to be zero for output, but LEDs won't flash unless I set them to one! :shock: I ran the MPLAB simulator, and: 2. bsf GPIO, GP1 will set GP1 bit to zero! :? 3. bcf GPIO, GP0 will set GP0 bit to one! :roll: Anyone has any idea what's going on? Here is the code: Code: org 0x00 goto init init bcf STATUS, RP0 ; Bank 0 clrf GPIO ; Init GPIO movlw 07h ; Set GP<2:0> movwf CMCON ; digital IO. Turn off comparator movlw b'00001111' ; GP<1:0> output GP<3:2> inputs movwf TRISIO ; bsf STATUS, RP0 ; Bank 1 main bsf GPIO, GP1 bcf GPIO, GP0 call delay bcf GPIO, GP1 bsf GPIO, GP0 call delay goto main delay ;;;;; delay routine ;;;;;;

13th March 2004, 05:49 AM	(permalink)
Nigel Goodwin	Without checking the datasheet, but based on other PIC's, the bank switching looks incorrent. TRIS is usually in bank 1, and GPIO in bank 0, you have them the other way. Which is why you think setting TRIS to 1 is making them an output - it's not, it's setting GPIO high. Then in the main part of the program you're toggling the TRIS bits, switching them from inputs to outputs.

13th March 2004, 12:52 PM	(permalink)
pike	yeah i just checked with the data sheet, GPIO is in bank 0, not bank 1. TRISIO is in bank 1. __________________ www.winpicprog.co.uk - Great PIC language tutorials.

14th March 2004, 04:08 AM	(permalink)
eirikr	Everything works now! Thanks a lot guys!