Software - Median of 3 bytes

Here is a short and fast routine to find the median (i.e. the middle value) of three bytes A, B, and C (A and B must be in consecutive memory locations):

; A, X, and Y registers assumed to be in 8-bit width mode
; for 65802 or 65816 microprocessors.

AB DS 2
C  DS 1

   LDX #1
   LDA AB
   CMP AB+1
   BCC .1
   LDA AB+1
   DEX
.1 CMP C
   BCS .2
   LDA AB,X
   CMP C
   BCC .2
   LDA C
.2 RTS

In this version, enter with the three bytes in the A, X, and Y registers; the median is returned in the accumulator.

   STX .M
   CMP .M
   BCS .1 ; branch if a >= m
   STA .M ; a is < x, so a -> m x -> a
   TXA
.1 CPY .M ; a is now >= m
   BCC .2 ; if y < m then m is the median
   STY .M ; y >= m, so m is smallest, so y -> m
   CMP .M ; the smaller of m and a is the median
   BCC .3 ; branch if a is smaller
.2 LDA .M
.3 RTS
.M DS  1  ; temporary storage