Post by thread:[PICLIST] bit adjustment

Hi PIClisters ! I've been learning a lot with you reading your posts. by now I have a trouble that I can't solve by myself, please can I'm writing a code to a remote control system with 4 channels, where the variable "channel" represents the "bit" that must be changed on PORTB. There is my code: ;channel assumes values from 0 to 3 movf portb, w ; make a copy of portB movwf sendreg ; on sendreg register " " " do something " btfss sendreg, channel goto _set ; this should invert the bit ;"channel" bcf sendreg, channel ; on sendreg register ====> but it ;doesn't do that !!! goto $ + 2 _set bsf sendreg, channel movf sendreg, w movwf portb return the instruction < bsf register, b > only accepts a literal on "b"??? how can I set a bit on a register (sendreg) using another pointer register (channel)??? any suggestions? thanks in advance, Eduardo. -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> Hi PIClisters ! > > I've been learning a lot with you reading your posts. by now I have a > trouble that I can't solve by myself, please can > > I'm writing a code to a remote control system with 4 channels, where the > variable "channel" represents the "bit" that must be changed on PORTB. The BSF, BCF, BTFSS and BTFSC instructions do only accept a literal for the bit number. So, you have to use logical instructions instead: First, you'll need a subroutine to convert from a channel number to a channel mask. This can be done as a lookup table or via direct logic. get_channel_mask: movf channel,W addwf PCL,F retlw 1 ; channel 0 retlw 2 ; channel 1 retlw 4 ; channel 2 retlw 8 ; channel 3 (standards warnings about setting PCLATH and spanning page boundaries apply to the above routine). Now: to set a PORTB bit for a channel: call get_channel_mask iorwf PORTB,F To clear a PORTB bit for a channel: call get_channel_mask xorlw 0xFF andwf PORTB,F To see if a bit is set for a channel: call get_channel_mask andwf PORTB,W skpz -- or-- skpnz Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

Sorry, I forgot the topic tag. ----- Original Message ----- From: Elopes <elopes_74KILLspamhotmail.com> To: pic microcontroller discussion list <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Sent: Tuesday, May 01, 2001 1:25 PM Subject: bit adjustment > Hi PIClisters ! > > I've been learning a lot with you reading your posts. by now I have a > trouble that I can't solve by myself, please can > > I'm writing a code to a remote control system with 4 channels, where the > variable "channel" represents the "bit" that must be changed on PORTB. There {Quote hidden}> is my code: > > ;channel assumes values from 0 to 3 > movf portb, w ; make a copy of portB > movwf sendreg ; on sendreg register > " > " > " do something > " > btfss sendreg, channel > goto _set ; this should invert the bit > ;"channel" > bcf sendreg, channel ; on sendreg register ====> but it > ;doesn't do that !!! > goto $ + 2 > _set > bsf sendreg, channel > movf sendreg, w > movwf portb > return > > the instruction < bsf register, b > only accepts a literal on "b"??? > how can I set a bit on a register (sendreg) using another pointer register > (channel)??? > any suggestions? > thanks in advance, > Eduardo. > > > -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

Thanks Bob Ammerman. You help me a lot. See how I coded the program: clrf acionador ;string to AND with portB movf canal, w movwf valor ;a channel copy movwf contador ; set the counter bsf status, c rlf acionador, f ; rotates the control word decfsz contador goto $ - 2 movf sendreg, w andwf acionador, w ;verify if the channel is on low or high level btfsc status, z goto _seta ; go to the set routine comf acionador, w andwf sendreg, w ;clear bit call ser_out ;put the value on portb return _seta movf acionador, w ;set bit iorwf sendreg, w call ser_out ;put the value on portb return -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestspam_OUTmitvma.mit.edu