Update mov_r_FAC1_MEM

src/basic/math_mov/bbd4.mov_r_FAC1_MEM.s

@@ -3,16 +3,21 @@
 ;; #LAYOUT# *   BASIC_0 #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
-;
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
 ; Math package - copy FAC1 to memory location, do not round
 ;
+; This is verified to be identical to the original Microsoft implementation where it was named MOVMF.
+;
 ; Input:
 ; - .X - address low byte
 ; - .Y - address high byte
 ;
 ; Output:
 ; - .A - FAC1 exponent
-;
+; - .Y - 0
+
 ; See also:
 ; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
 ; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
@@ -20,7 +25,25 @@
 
 mov_r_FAC1_MEM:
 	
-	; Start by rounding FAC1
-
-	jsr round_FAC1
-	jmp mov_FAC1_MEM
+    jsr round_FAC1
+    stx INDEX+0
+    sty INDEX+1
+    ldy #4
+    lda FAC1_mantissa+3
+    sta (INDEX),y
+    dey
+    lda FAC1_mantissa+2
+    sta (INDEX),y
+    dey
+    lda FAC1_mantissa+1
+    sta (INDEX),y
+    dey
+    lda FAC1_sign
+    ora #$7F
+    and FAC1_mantissa
+    sta (INDEX),y
+    dey
+    lda FAC1_exponent
+    sta (INDEX),y
+    sty FACOV
+    rts