Post by thread:[PIC] : FSR & INDF ?

within an interupt, I am spitting out data serially on a I2C (this is based on the AN734 app note). I can get it to send out multiple bytes, recieve data, etc For development purposes, I have a counter that just increments everytime it drops into the routine so I can see the data come out as I expect it to. However, I want to use the counter to point to a register location. In other words, I have 10 registers and I want to sequence thru the locations everytime I do a read. Sounds simple, but looking for a pointer and sorta assume that using the FSR might be the right approach? _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Thu, 4 Apr 2002 09:15:46 -0700, Micro Eng wrote: >within an interupt, I am spitting out data serially on a I2C (this is based >on the AN734 app note). > >I can get it to send out multiple bytes, recieve data, etc > >For development purposes, I have a counter that just increments everytime it >drops into the routine so I can see the data come out as I expect it to. > >However, I want to use the counter to point to a register location. In other >words, I have 10 registers and I want to sequence thru the locations >everytime I do a read. Sounds simple, but looking for a pointer and sorta >assume that using the FSR might be the right approach? > Good assumption. That's exactly what the FSR and INDF will do for you. Just be sure to preserve FSR on entry to your interrupt and restore it on exit. And, no, please don't ask where this (not particularly brilliant) piece of insight came from. :=) Regards, Bob -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> within an interupt, I am spitting out data serially on a I2C > (this is based on the AN734 app note). > > I can get it to send out multiple bytes, recieve data, etc > > For development purposes, I have a counter that just > increments everytime it drops into the routine so I can see > the data come out as I expect it to. > > However, I want to use the counter to point to a register > location. In other words, I have 10 registers and I want to > sequence thru the locations everytime I do a read. Sounds > simple, but looking for a pointer and sorta assume that using > the FSR might be the right approach? You bet, INDF and FSR are used for indirect addressing (i.e. pointers) in our beloved PICs... Works great. spam_OUTnickTakeThisOuTveys.com | http://www.veys.com/nick -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Micro Eng, A point of detail. You're putting a space between [PIC] and : so the messages aren't getting onto the PIC discussion group needs to be [PIC]: FSR is indeed the pointer, note you can set up a variable set say... CBLOCK 0x20 Variable0 Variable1 Variable2 Variable3 ENDC ; obviously Variable0 starts at address h20 but you can have it elsewhere although the following code relies on your variable array starting at n0 (and you need to think about bits too - see below*). movlw Variable0, ; get the address of Variable0 into w movwf FSR ; put address from above into FSR xyz: movf INDF, w ; get contents of Variable0 into w ; ... more code?? ; ... more code?? incf FSR, f ; increment the FSR pointer btfss FSR, 2 ; * test bit 2 to see if it's set (ie FSR has inc'd to 4) ; alter the above line or do more complicated test on FSR bits or value. You could start Variable0 at a location such that 10 inc's will result in 4 being set. goto xyz ; not done yet so do again next line of code I can be hired if you want any code written! Ted Mawson (unemployed) {Original Message removed}