Post by thread:[PIC]: Changing RB0 INT edge trigger

Hi all, Thanks for all the help with the interupt problms. I finally got them working. Guess I'll have to rember OPTION_REG is in Bank1! Doh! I have just realised that I need the RB0 interupt to trigger on both edges! So I have decided to change the trigger edge on the fly. My question is: Is this the fastest/most efficient way to do this? BANK1 btfsc OPTION_REG,INTEDG ; IF already set to +ve edge trigger goto SET_NEG_EDGE ; Goto set -ve dege trigger bsf OPTION_REG,INTEDG ; ELSE set +ve edge trigger goto EDGE_SET ; Finished SET_NEG_EDGE bcf OPTION_REG,INTEDG ; Set -ve edge trigger EDGE_SET ; Finished BANK0 I seem to remember being able to XOR a file with another to do someting. Is that a way change just one bit. I could never get my head round it. Could someone explain the whole XOR thing. Thanks Graham _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

----- Original Message ----- From: "Graham North" <spam_OUTgs_piclistTakeThisOuTHOTMAIL.COM> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Saturday, April 28, 2001 9:04 AM Subject: [PIC]: Changing RB0 INT edge trigger > Hi all, > > Thanks for all the help with the interupt problms. I finally got them > working. > Guess I'll have to rember OPTION_REG is in Bank1! Doh! Been there, done that. <GRIN> > I have just realised that I need the RB0 interupt to trigger on both edges! > So > I have decided to change the trigger edge on the fly. My question is: > > Is this the fastest/most efficient way to do this? > > BANK1 > > btfsc OPTION_REG,INTEDG ; IF already set to +ve edge trigger {Quote hidden}> goto SET_NEG_EDGE ; Goto set -ve dege trigger > bsf OPTION_REG,INTEDG ; ELSE set +ve edge trigger > goto EDGE_SET ; Finished > > SET_NEG_EDGE > > bcf OPTION_REG,INTEDG ; Set -ve edge trigger > > EDGE_SET ; Finished > > BANK0 > > I seem to remember being able to XOR a file with another to do someting. Is > that a way change just one bit. I could never get my head round it. Could > someone > explain the whole XOR thing. Just like OR except 1(XOR)1 ->0 That's pretty much it. 0 1 ----------- 0 | 0 1 1 | 1 0 WARNING: Untested code ahead ;-) But this is the fastest way I know of. BANK1 movlw b'01000000' load bit mask for INTEDG (bit 6) xorwf OPTION_REG, F flip the bit, leaving result in OPTION_REG BANK0 Of course you are left with no idea of which state the bit is currently in, it just gets flipped. {Quote hidden}> > Thanks > > Graham > _________________________________________________________________________ > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Hi all, > > Thanks for all the help with the interupt problms. I finally got them > working. > Guess I'll have to rember OPTION_REG is in Bank1! Doh! > > I have just realised that I need the RB0 interupt to trigger on both edges! > So > I have decided to change the trigger edge on the fly. My question is: > > Is this the fastest/most efficient way to do this? > > BANK1 > > btfsc OPTION_REG,INTEDG ; IF already set to +ve edge trigger {Quote hidden}> goto SET_NEG_EDGE ; Goto set -ve dege trigger > bsf OPTION_REG,INTEDG ; ELSE set +ve edge trigger > goto EDGE_SET ; Finished > > SET_NEG_EDGE > > bcf OPTION_REG,INTEDG ; Set -ve edge trigger > > EDGE_SET ; Finished > > BANK0 > > I seem to remember being able to XOR a file with another to do someting. Is > that a way change just one bit. I could never get my head round it. Could > someone > explain the whole XOR thing. > > Thanks > > Graham Yep, XOR is the trick. Try this: BANK1 movlw 1 << INTEDG xorwf OPTION_REG,F BANK0 The 'movlw 1 <<INTEDG' sets W to contain a 1 bit in the position corresponding to the INTEDG bit in the OPTION_REG and zero bits everyplace else. The 'xorwf OPTION_REG,F' computes: OPTION_REG = OPTION_REG xor W Now 'xor' is defined as follows: 0 xor 0 = 0 0 xor 1 = 1 1 xor 0 = 1 1 xor 1 = 0 Note that an xor with zero leaves a value unchanged, but an xor with one complements it. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Dear Graham North, Graham North <gs_piclistKILLspamHOTMAIL.COM> on 2001-04-28 09:04:35 AM mentioned: > I have just realised that I need the RB0 interupt to trigger on both edges! > So I have decided to change the trigger edge on the fly. Michael Brown's code looks good at first glance. On the 16F87x, RB4 and RB5 can be set up to "interrupt on change". Maybe it would be simpler to use one of those rather than RB0 ? -- David Cary -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu