Post by thread:comparison routine

<x-flowed>Esteemed PIC Gurus: Does anyone have a favorite way to do a window comparison on an A/D result? Seems to me there was one here a week ago, but it has eluded me. What I want to do is to insert code in an existing loop that will set an alarm output pin if the A/D result falls outside the window; set another pin high if it is below the hard-coded lower limit, set a different pin if it is above the upper limit, and continue on without setting any of the three if the result is within the window. TIA, Reg Neale </x-flowed>

Reginald Neale wrote: > > Esteemed PIC Gurus: > > Does anyone have a favorite way to do a window comparison on an A/D > result? Seems to me there was one here a week ago, but it has eluded > me. > > What I want to do is to insert code in an existing loop that will set > an alarm output pin if the A/D result falls outside the window; set > another pin high if it is below the hard-coded lower limit, set a > different pin if it is above the upper limit, and continue on without > setting any of the three if the result is within the window. > > TIA, > Reg Neale movf ADres,w sublw UpLimit btfss status,c goto TooHigh movlw LoLimit subwf ADres,w btfss status,c goto TooLow -- Best regards Tony http://www.picnpoke.com spam_OUTsalesTakeThisOuTpicnpoke.com

On Thu, 23 Mar 2000, Tony Nixon wrote: {Quote hidden}> Reginald Neale wrote: > > > > Esteemed PIC Gurus: > > > > Does anyone have a favorite way to do a window comparison on an A/D > > result? Seems to me there was one here a week ago, but it has eluded > > me. > > > > What I want to do is to insert code in an existing loop that will set > > an alarm output pin if the A/D result falls outside the window; set > > another pin high if it is below the hard-coded lower limit, set a > > different pin if it is above the upper limit, and continue on without > > setting any of the three if the result is within the window. > > > > TIA, > > Reg Neale > > movf ADres,w > sublw UpLimit > btfss status,c > goto TooHigh > > movlw LoLimit > subwf ADres,w > btfss status,c > goto TooLow > If you're comparing against constants, why not do this: movf ADres,w sublw UpLimit ;W = UpLimit - ADres skpc goto TooHigh sublw UpLimit-LoLimit ;W = ADres - LoLimit skpc goto TooLow (You save a whole instruction!) Example: ADres LoLimit UpLimit (Up-AD) (AD-Lo) ------------------------------------------------------ 9 4 10 10-9=>1,C=1 6-1=>5,C=1 11 4 10 10-11=>ff,C=0 ---- 2 4 10 10-2=>8,C=1 6-8=>fe,C=0 C-Code: GoldiLocks(unsigned char ADres) { if(ADres>HiLimit) TooHigh(); else if(ADres < LoLimit) TooLow(); else JustRight(); } Scott

Reginald Neale <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> wrote: > Does anyone have a favorite way to do a window comparison on an > A/D result? .... What I want to do is to insert code in an existing > loop that will set an alarm output pin if the A/D result falls > outside the window; set another pin high if it is below the > hard-coded lower limit, set a different pin if it is above the > upper limit, and continue on without setting any of the three if > the result is within the window. Reg: Try this; I haven't even assembled it, let alone tested it, but it SHOULD work... MOVF ADRES,W ADDLW 256-UPPER ;These 4 lines were written by ADDLW (UPPER-LOWER)+1 ;a smart guy named Eric Smith. SKPNC ; GOTO DONE ; ;Our A/D result was outside the [LOWER-UPPER] window. BSF ALARMPIN ;Set the ALARM pin. ADDLW LOWER-1 ;Was ADRES too low? SKPC ;If so, skip ahead. BSF HIGHPIN ;Otherwise, set the HIGHPIN pin. SKPNC ;If ADRES was too high, skip ahead. BSF LOWPIN ;Otherwise, set the LOWPIN pin. DONE: -Andy === Andrew Warren - fastfwdKILLspamix.netcom.com === Fast Forward Engineering - San Diego, California === http://www.geocities.com/SiliconValley/2499

John Orhan <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> wrote: > Could I ask what the intruction 'SKPNC' does? Is it skip if not > carry? Forgive my ignorance but I have not seen it before. John: Yeah, it means "skip if the carry flag is clear"; it's equivalent to BTFSC STATUS,C and it's always been supported by MPASM, although it hasn't always been documented. The latest MPASM/MPLAB User's Guides contain a table showing this and all other pseudo-ops understood by MPASM; here's the list: PIC16CXX SPECIAL INSTRUCTION MNEMONICS Name Mnemonic Equivalent Status Operation(s) Clear Carry CLRC BCF 3,0 - Clear Digit Carry CLRDC BCF 3,1 - Set Digit Carry SETDC BSF 3,1 - Clear Zero CLRZ BCF 3,2 - Set Zero SETZ BSF 3,2 - Skip on Carry SKPC BTFSS 3,0 - Skip on No Carry SKPNC BTFSC 3,0 - Skip on Digit Carry SKPDC BTFSS 3,1 - Skip on No Digit Carry SKPNDC BTFSC 3,1 - Skip on Zero SKPZ BTFSS 3,2 - Skip on Non Zero SKPNZ BTFSC 3,2 - Test File TSTF f MOVF f,1 Z Move File to W MOVFW f MOVF f,0 Z Negate File NEGF f,d COMF f,1 INCF f,d Z Add Carry to File ADDCF f,d BTFSC 3,0 INCF f,d Z Subtract Carry from File SUBCF f,d BTFSC 3,0 DECF f,d Z Add Digit Carry to File ADDDCF f,d BTFSC 3,1 INCF f,d Z Subtract Digit SUBDCF f,d BTFSC 3,1 Carry from File DECF f,d Z Branch B k GOTO k - Branch on Carry BC k BTFSC 3,0 GOTO k - Branch on No Carry BNC k BTFSS 3,0 GOTO k - Branch on Digit Carry BDC k BTFSC 3,1 GOTO k - Branch on No Digit Carry BNDC k BTFSS 3,1 GOTO k - Branch on Zero BZ k BTFSC 3,2 GOTO k - Branch on Non Zero BNZ k BTFSS 3,2 GOTO k - Call across page boundary LCALL k BCF 3,5 or BSF 3,5 BCF 3,6 or BSF 3,6 CALL k By the way, don't bother using the "LCALL" pseudo-op... Since it doesn't restore the code-page bits after the CALL, it's sorta useless. Also, be careful with the pseudo-ops that assemble to two instructions; constructs like the following, for instance, will cause you great pain and suffering: ; DON'T DO THIS! BTFSS FLAGS,SWITCH ;If the switch is pressed, skip ahead. NEGF REG ;Otherwise, negate the REG register. -Andy === Andrew Warren - fastfwdspam_OUTix.netcom.com === Fast Forward Engineering - San Diego, California === http://www.geocities.com/SiliconValley/2499