Masking Upper Nibble - Electronic Circuits Projects Diagrams Free

Suraj143 · 15th August 2008, 03:23 AM

Hi I need to mask the upper nibble & must not do any harm to the lower nibble.

But this code never work.

Code:

	movf	Data,W
	andlw	b'11110000'
	iorwf	PORTB,F

But this code works but corrupting lower nibble.

Code:

	movf	Data,W
	andlw	b'11110000'
	movwf	PORTB,F

futz · 15th August 2008, 03:52 AM

Quote:

Originally Posted by Suraj143

Hi I need to mask the upper nibble & must not do any harm to the lower nibble.

But this code works but corrupting lower nibble.

Code:

	movf	Data,W
	andlw	b'11110000'
	movwf	PORTB,F

That's because you should use AND to clear, or mask, the upper nibble - not the lower nibble. Like this:

Code:

	andlw	b'00001111'

This will zero out the upper nibble and leave the lower nibble exactly the way it was.

kchriste · 15th August 2008, 03:57 AM

Do you wish to transfer the upper nibble of Data to the upper nibble of PORTB without disturbing the lower nibble in either?

Suraj143 · 15th August 2008, 04:06 AM

Quote:

Originally Posted by kchriste

Do you wish to transfer the upper nibble of Data to the upper nibble of PORTB without disturbing the lower nibble in either?

Exactly this is what I need to do.

futz · 15th August 2008, 04:13 AM

Quote:

Originally Posted by Suraj143

Exactly this is what I need to do.

Then first move Data to a temp variable or W and mask the lower nibble. Then mask the upper nibble of PORTB (maybe move it to a temporary variable first). Then OR them together.

Maybe there's a simpler way?

Suraj143 · 15th August 2008, 04:19 AM

Quote:

Originally Posted by futz

Then first move Data to a temp variable or W and mask the lower nibble. Then mask the upper nibble of PORTB (maybe move it to a temporary variable first). Then OR them together.

Maybe there's a simpler way?

Code:

	movf	Data,W
	andlw	b'00001111'
	????	????
	iorwf	PORTB,F

futz · 15th August 2008, 04:29 AM

Code:

	movf	Data,W
	andlw	b'11110000'
	movwf	temp1
	movf	PORTB,w
	andlw	b'00001111'
	iorwf	temp1,w
	movwf	PORTB

Hmm... Is that right? Just quickly banged it out. Can't test it quickly.

Suraj143 · 15th August 2008, 04:33 AM

Quote:

Originally Posted by futz

Code:

	movf	Data,W
	andlw	b'11110000'
	movwf	temp1
	movf	PORTB,w
	andlw	b'00001111'
	iorwf	temp1,w
	movwf	PORTB

Hmm... Is that right? Just quickly banged it out. Can't test it quickly.

OK thanks for your help.It will work.

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15th August 2008, 03:23 AM	(permalink)
Suraj143	Masking Upper Nibble Hi I need to mask the upper nibble & must not do any harm to the lower nibble. But this code never work. Code: movf Data,W andlw b'11110000' iorwf PORTB,F But this code works but corrupting lower nibble. Code: movf Data,W andlw b'11110000' movwf PORTB,F

15th August 2008, 03:57 AM	(permalink)
kchriste	Do you wish to transfer the upper nibble of Data to the upper nibble of PORTB without disturbing the lower nibble in either? __________________ --- The days of the digital watch are numbered. ---

15th August 2008, 04:29 AM	(permalink)
futz	Code: movf Data,W andlw b'11110000' movwf temp1 movf PORTB,w andlw b'00001111' iorwf temp1,w movwf PORTB Hmm... Is that right? Just quickly banged it out. Can't test it quickly. __________________ ========================= Futz's Microcontrollers & Robotics =========================