What mean : tris PORTA

savnik · Feb 14, 2007

I have the below code:

---------------------------------------------------
trisabuf VAR BYTE
movlw 0x10 ; 00010000 - RA4 is entry
movwf trisabuf
---------------------------------------------------
bsf trisabuf,3
movf trisabuf,W
tris PORTA
----------------------------------------------------

What mean : tris PORTA ;
This mean that PORTA = trisabuf ;

Papabravo · Feb 14, 2007

On older versions of the PIC architecture there was a specific instruction that loaded the the TRIS register. On the newer versions you use a move instruction just like every other file register. If you read the datasheets really carefully they discourage the use of the dedicated instruction in favor of the more generic move instruction

savnik · Feb 14, 2007

Papabravo said:
On older versions of the PIC architecture there was a specific instruction that loaded the the TRIS register. On the newr versions you use a move instruction just like every other file register. If you read the datasheets really carefully they discourage the use of the dedicated instruction in favor of the more generic move instruction

Yes is for PIC16C54

Gayan Soyza · Feb 15, 2007

bsf trisabuf,3
movf trisabuf,W
tris PORTA

Simply You can use this line to turn on RA3 on PORTA

Code:

BSF	PORTA,3

Papabravo · Feb 15, 2007

savnik said:
Yes is for PIC16C54

On such an old device there is no alternative to the TRIS instruction because that register does not have a valid register file address.

savnik · Feb 15, 2007

I found:

bcf _trisabuf,3
bsf STATUS, RP0
movf _trisabuf,W
movwf TRISA
bcf STATUS, RP0

I use for pic16f628a

Nigel Goodwin · Feb 15, 2007

savnik said:
I found:

bcf _trisabuf,3
bsf STATUS, RP0
movf _trisabuf,W
movwf TRISA
bcf STATUS, RP0

I use for pic16f628a

Is there some reason for using '_trisabuf'?, instead of just

Code:

	   bsf	 STATUS, RP0     
	   bcf   TRISA, 3            
	   bcf	 STATUS, RP0

savnik · Feb 16, 2007

You are right
Thank you

What mean : tris PORTA

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