Post by thread:PORTA Question!yal@CAPITALNET

Hi All PICers ! > From: Jean-Francois Joly <spam_OUTjolyalTakeThisOuTCAPITALNET.COM> > Subject: PORTA Question! > Hello everyone! > > I would like to make a little program that sends a high on > the RA0 pin to light up a LED. I think it should be simple > enought, but because this is my first attempt in programming > a PIC, Im not to sure... > > This is the main part of the program. If something is wrong > or missing, please tell me! > > BSF PORTA, RA0 ; Want to put 1 on RA0 pin > BSF TRISA, TRISA0 ; Output a high on RA0 pin ^^^ bcf, at first. What about ROM PAGE selecting ? PORTA is on the 0-page, but TRISA - on 1st once. You must write: bcf porta,ra0 bsf status,RP0 bsf trisa,0 bcf status,RP0. More better - to use macros and defines, for example: ; #define A0_ON bsf porta,0 #define A0_OFF bcf porta,0 #define A0_INP bsf trisa & 0x7f,0 #define A0_OUT bcf trisa & 0x7f,0 ; PAGESET macro pagenum if pagenum == 1 bsf status,RP0 else bcf status,RP0 endif endm ; ;After that your program looks like : ; A0_ON PAGESET 1 A0_OUT PAGESET 0 ; > Would this work? See before :-) > Does it send the signal to the pin at the > same moment that I set in the TRISA register pin RA0 as > output? Yes, of course. Best Wishes, Alex Torres. Kharkov, Ukraine, exUSSR. E-Mail To : .....altorKILLspam@spam@cook.kharkov.ua via InterNet or 2:461/28 via FidoNet --- GoldED 2.50.A0531+

Hello! > bcf porta,ra0 > bsf status,RP0 ; Change bank 1 > bsf trisa,0 > bcf status,RP0 ; Change back to bank 0 Why do you change back to bank 0 after? > > Does it send the signal to the pin at the > > same moment that I set in the TRISA register pin RA0 as > > output? > > >Yes, of course. But what if I set the direction first with the TRIS register like Ed Tood told me in his last message and then I set the output latch? TTYL! Jean --------------- Jean-Francois & Alain Joly jolyalKILLspamcapitalnet.com

> > Hello! > > > bcf porta,ra0 > > bsf status,RP0 ; Change bank 1 > > bsf trisa,0 > > bcf status,RP0 ; Change back to bank 0 > > Why do you change back to bank 0 after? Because you want to make sure that future accesses to the ports and registers are in bank 0. It's good programming practice. {Quote hidden}> > > > Does it send the signal to the pin at the > > > same moment that I set in the TRISA register pin RA0 as > > > output? > > > > > >Yes, of course. > > But what if I set the direction first with the TRIS register like Ed Tood > told me in his last message and then I set the output latch? Then whatever value is in the output latch when you set the TRIS register will appear on the pin briefly until it's changed. By setting the latch first, there's no possibility of a glitch. BAJ

Hi! >> > bcf porta,ra0 >> > bsf status,RP0 ; Change bank 1 >> > bsf trisa,0 >> > bcf status,RP0 ; Change back to bank 0 >> >> Why do you change back to bank 0 after? > >Because you want to make sure that future accesses to the ports and >registers are in bank 0. It's good programming practice. Oh ok... and when you execute the BCF PORTA,RA0 instruction on the first line, your supposing that we are already in bank 0 'cause PORTA is in bank 0? >Then whatever value is in the output latch when you set the TRIS register >will appear on the pin briefly until it's changed. By setting the latch >first, there's no possibility of a glitch. Cool! Well, thanks a lot for your help and all the people who helped me with that PORTA Question! Jean-Francois --------------- Jean-Francois & Alain Joly .....jolyalKILLspam.....capitalnet.com

> > Hi! > > >> > bcf porta,ra0 > >> > bsf status,RP0 ; Change bank 1 > >> > bsf trisa,0 > >> > bcf status,RP0 ; Change back to bank 0 > >> > >> Why do you change back to bank 0 after? > > > >Because you want to make sure that future accesses to the ports and > >registers are in bank 0. It's good programming practice. > > Oh ok... and when you execute the BCF PORTA,RA0 instruction on the first > line, your supposing that we are already in bank 0 'cause PORTA is in bank 0? Precisely. > > > >Then whatever value is in the output latch when you set the TRIS register > >will appear on the pin briefly until it's changed. By setting the latch > >first, there's no possibility of a glitch. > > Cool! Well, thanks a lot for your help and all the people who helped me with > that PORTA Question! You're welcome. Hope to see more of your questions on the list. BAJ