Post by thread:%best way for range checking ?%

Hi, I`m need to do something in assembler like the following pseudo code does: unsigned char a; // Byte holds value to be compared unsigned char state; // Byte holds kind of result const state_1 = 1; const state_2 = 2; ( ... ) case ((a < const1) AND (a > const2)) then state = state_1 else case ((a < const3) AND (a > const4)) then state = state_2 else case ((a < const5) AND (a > const64)) then state = state_3 default: state = err; The "<" and ">" could also be ">=" or "<=". The primary need is to check for "a" being within a range. Target Pic 16C84 Ideas ?

Hi, I use a macro for range checking which will branch when W is not between two constants. This could be used as follows: bwNotBetween MACRO x,y,label addlw -((y)+1) ; make high value -1, should borrow. bc label ; branch above our range (no borrow) addlw (y)+1-(x) ; make low value 0, should carry here. bnc label ; branch if below our range ENDM .. movf a,w bwNotBetween const1, const2, Label_a movlw state_1 movwf state goto exit Label_a: movf a,w bwNotBetween const1, const2, Label_b ... You probably can hard code it in a few less instructions. Chip. Stefan Sczekalla-Waldschmidt wrote: {Quote hidden}>Hi, > >I`m need to do something in assembler like the following pseudo code >does: > > unsigned char a; // Byte holds value to be compared > unsigned char state; // Byte holds kind of result > const state_1 = 1; > const state_2 = 2; > ( ... ) > > case ((a < const1) AND (a > const2)) > then state = state_1 > else case ((a < const3) AND (a > const4)) > then state = state_2 > else case ((a < const5) AND (a > const64)) > then state = state_3 > default: state = err; > >The "<" and ">" could also be ">=" or "<=". The primary need >is to check for "a" being within a range. > >Target Pic 16C84 > >Ideas ?

Stefan Sczekalla-Waldschmidt <spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU> wrote: {Quote hidden}> I`m need to do something in assembler like the following pseudo code > does: > > unsigned char a; // Byte holds value to be > compared > unsigned char state; // Byte holds kind of result > const state_1 = 1; > const state_2 = 2; > ( ... ) > > case ((a < const1) AND (a > const2)) > then state = state_1 > else case ((a < const3) AND (a > const4)) > then state = state_2 > else case ((a < const5) AND (a > const64)) > then state = state_3 > default: state = err; > > The "<" and ">" could also be ">=" or "<=". The primary need > is to check for "a" being within a range. > > Target Pic 16C84 Stefan: Use Eric Smith's method: addlw 255-upper addlw (upper-lower)+1 bc inrange In your specific case, the code would look like this (I'm assuming that "a" is stored in a register called "a_value", and that your comparisons are ">=" and "<=": movlw state_1 ;Assume that we'll set movwf state ;state to state_1. movf a_value,w ;If const2 <= a <= const1, addlw 255-const1 ;exit with state = state_1. addlw (const1-const2)+1 ; bc done ; movlw state_2 ;Otherwise, assume that movwf state ;we'll set state to state_2. movf a_value,w ;If const4 <= a <= const3, addlw 255-const3 ;exit with state = state_2. addlw (const3-const4)+1 ; bc done ; movlw state_3 ; etc... movwf state ; movf a_value,w ; addlw 255-const5 ; addlw (const5-const6)+1 ; bc done ; movlw state_err ;Otherwise, movwf state ;state = state_err. done: .... -Andy === Andrew Warren - .....fastfwdKILLspam@spam@ix.netcom.com === Fast Forward Engineering - Vista, California === http://www.geocities.com/SiliconValley/2499

Hi, I think you wanted to check whether a falls within any of ranges, i. e. case ((a => const1) AND (a <= const2)) instead of what you have written. If I guess it right, here is a macro I use to reduce the generated code size for PIC Basic Pro. ;**************************************************************** ;* MYLIB.LIB * ;* * ;* By : Dr. Imre B‡rtfai * ;* Notice : Copyright (c) 1998 Dr. Imre B‡rtfai * ;* All Rights Reserved * ;* Date : 07/16/98 * ;* Version : 1.00 * ;* Revision : a * ;* Notes : * ;**************************************************************** NOLIST ;**************************************************************** ;* Utility macros * ;**************************************************************** ;**************************************************************** ;* INTVAL?BCC : Macro - check whether a var falls into an intval* ;* * ;* Input : var = file register * ;* : lower = lower bound of interval * ;* : upper = upper bound of interval * ;* : label = label to be jump if var out of interval* ;* Output : none * ;* : W = var - lower * ;* : RWO = W (if defined) * ;* * ;* Notes : quick and dirty version; * ;* : no page boundary crossing handled yet * ;**************************************************************** INTVAL?BCC macro var,lower,upper,label,RWO if lower >= upper error 'Lower bound exceeds upper bound in INTVAL?BCC' else movf var,W ; fetch the value addlw ~upper ; check whether out ouf upper bound jc label addlw upper-lower+1 ; check whether out of lower bound jnc label ifnb RWO movwf RWO endif endif endm ;**************************************************************** LIST The 'label' must point in your case to the next 'case'. I hope I have helped. Imre On Wed, 5 Aug 1998, Stefan Sczekalla-Waldschmidt wrote: {Quote hidden}> Hi, > > I`m need to do something in assembler like the following pseudo code > does: > > unsigned char a; // Byte holds value to be compared > unsigned char state; // Byte holds kind of result > const state_1 = 1; > const state_2 = 2; > ( ... ) > > case ((a < const1) AND (a > const2)) > then state = state_1 > else case ((a < const3) AND (a > const4)) > then state = state_2 > else case ((a < const5) AND (a > const64)) > then state = state_3 > default: state = err; > > The "<" and ">" could also be ">=" or "<=". The primary need > is to check for "a" being within a range. > > Target Pic 16C84 > > Ideas ? > >

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