Post by thread:[PIC] 12f629 bsf function

I am trying to set selected bits in GPIO using bsf GPIO, n where n can be 0,1,2,4 The selected bit gets set ok but any bit which is already on is cleared at the same time. Why is this - and how should I do to set and clear bits individually? test code: bit 0 blinks once and then bit 1 is set: bsf GPIO,0 call delay bsf GPIO,1 loop goto loop Goran

Goran Hosinsky wrote : > test code: bit 0 blinks once and then bit 1 is set: > > bsf GPIO,0 > call delay > bsf GPIO,1 > loop goto loop That can't be a full test-case ! What is connected to the pins ? And how ? How long is "delay" ? What does "blinks" mean ? Regards, Jan-Erik.

> I am trying to set selected bits in GPIO using > bsf GPIO, n where n can be 0,1,2,4 > The selected bit gets set ok but any bit which is > already on is cleared at the same time. Why is > this google (or search http://www.piclist.com) for read-modify-write problem I have probably mentioned and explained it somewhere in http://www.voti.nl/swp. > - and how should I do to set and clear bits > individually? use a shadow register (google will explain) Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products docent Hogeschool van Utrecht: http://www.voti.nl/hvu

Goran: Wouter explains it well Use a shadow register as below For instance:- Bsf PORT_A,0 ; PORT_A is the name of the shadow register for GPIO (A) Movfw PORT_A ; get the shadow reg Movwf GPIO ; then transfer the whole reg to the port Call delay Bsf PORT_A,1 Movfw PORT_A Movwf GPIO Call delay Bcf PORT_A,0 ; PORT_A is the name of the shadow register for GPIO (A) Movfw PORT_A ; get the shadow reg Movwf GPIO ; then transfer the whole reg to the port Call delay Bcf PORT_A,1 Movfw PORT_A Movwf GPIO Call delay Goto $ ; stop here This will fix any read modify write problems that maybe causing the pins to become unset its straight line code and can be simplified by the following Bsf PORT_A,0 ;on PORT_A is the name of the shadow register for GPIO (A) Call Update_port Bsf PORT_A,1 Call Update_port Bcf PORT_A,0 ;off Call Update_port Bcf PORT_A,1 Call Update_port Update_port Movfw PORT_A ; get the shadow reg Movwf GPIO ; then transfer the whole reg to the port Goto delay Goto $ ; stop here The two code bits do the same thing but the second set uses less program space the example turns on led 0 then led 1 then turns off led 0 then led 1 but uses the update port section four times. Regards Steve {Original Message removed}

At 10:51 AM 5/24/2006, Goran Hosinsky wrote: >I am trying to set selected bits in GPIO using >bsf GPIO, n where n can be 0,1,2,4 >The selected bit gets set ok but any bit which is >already on is cleared at the same time. Why is >this - and how should I do to set and clear bits >individually? >test code: bit 0 blinks once and then bit 1 is set: > > bsf GPIO,0 > call delay > bsf GPIO,1 >loop goto loop Hi there, Goran. I suspect that your problem is caused by the default setting in the CMCON register. The default power-up settings configure ports GPIO,0 and GPIO,1 as analog inputs. This means that they will always read as a logic 0 when read. Others have mentioned R-M-W problems and that is exactly what this is. However, the easy cure (assuming that you are using the internal RC oscillator at 4 MHz) is to simply load the value of 0x07 into register CMCON. Hope this helps. dwayne -- Dwayne Reid <spam_OUTdwaynerTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 22 years of Engineering Innovation (1984 - 2006) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email.