*``````````````````````````````*
* RAND16 : 16BIT RANDOM NUMBER *
*-                            -*
* GENERATE A 16BIT PSEUDO-     *
* RANDOM NUMBER AND RETURN IT  *
* IN Y,X (LOW, HIGH).          *
*                              *
* ORIGINAL AUTHOR IS WHITE     *
* FLAME, AS SHARED ON          *
* CODEBASE64.                  *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*-                            -*
* ENTRY                        *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HIGH BYTE OF RETURN ADDRESS  *
*-                            -*
* EXIT                         *
*                              *
* .Y = HIGH BYTE OF PRODUCT    *
* .X = LOW BYTE OF PRODUCT     *
* .A = LOW BYTE OF PRODUCT     *
*                              *
* [RETURN] = RESULT (2 BYTES)  *
* [RETLEN] = 2 (RESULT LENGTH) *
*-                            -*
* NOTE: THERE ARE 2048 MAGIC   *
* NUMBERS THAT COULD BE EOR'D  *
* TO GENERATE A PSEUDO-RANDOM  *
* PATTERN THAT DOESN'T REPEAT  *
* UNTIL 65535 ITERATIONS. TOO  *
* MANY TO LIST HERE, BUT SOME  *
* ARE: $002D, $1979, $1B47,    *
* $41BB, $3D91, $B5E9, $FFEB   *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
RAND16
*
         LDA   RNDL
         STA   :SEED
         LDA   RNDH
         STA   :SEED+1
*
         LDA   :SEED
         BEQ   :LOW0
*
** DO A NORMAL SHIFT
*
         ASL   :SEED
         LDA   :SEED+1
         ROL
         BCC   :NOEOR
:DOEOR                    ; HIGH BYTE IN A
         EOR   #>$0369
         STA   :SEED+1
         LDA   :SEED
         EOR   #<$0369
         STA   :SEED
         JMP   :EXIT
:LOW0
         LDA   :SEED+1
         BEQ   :DOEOR
         ASL
         BEQ   :NOEOR
         BCS   :DOEOR
:NOEOR
         STA   :SEED+1
:EXIT    LDX   :SEED+1
         LDY   :SEED
         STY   RETURN
         STX   RETURN+1
         LDA   #2
         STA   RETLEN
         RTS
*
** DATA
*
:SEED    DS    2
*