The original question was, to find a routine for min and max of four
numbers. The bubble sort is one, here is another.

19 words, no bubble sort, NO STACK USE (can inline). Uses 1 aux. register,
leaves input data unchanged, output in Fmin and Fmax. Faster than Andy
Warren's bubble sort ? Expands to more than 4 values to be analyzed (set
LAST...).

Run time: 20 + (LAST-1) * 14 -> 62T constant run time

(Andy Warren's bubble sort takes a shorter, but variable time, and uses
the stack - not an option in an ISR on a 14 bit core and NON option on 12
bit cores. Avg. time for his ORDER is 5.5 T. His run time is: 9.5 + 15 +
16.5 + 2 ~= 43 (+/- 3T) I think).

(BEWARE UNTESTED CODE)

LAST db 4

;; find lowest and highest value from a vector of bytes between FSR and
;; FSR + LAST, sort in Fmin and Fmax, destroys Fcounter, no stack
MinMax:
  movlw LAST
  movwf Fcounter

  clrf  Fmax
  incf  Fmax,w
  movwf Fmin

loop:
  movf  INDF,w
  subwf Fmax,w  ;; Fmax - INDF < 0 ? C = 0
  movf  INDF,w
  btfss STATUS,C
  movwf Fmax

  movf  Fmin,w
  subwf INDF,w  ;; INDF - Fmin < 0 ? C = 0
  movf  INDF,w
  btfss STATUS,C
  movwf Fmin

  incf  FSR,f

  decfsz Fcounter,f
  goto   loop

  retlw 0

Peter

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