random seed initialization added, tweaked sequence generation

c64/basic/math/e09a.rnd_A.s

@@ -0,0 +1,26 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Random number generator routine
+//
+// Input:
+// - .A (0 - reinitialize the seed with random value, $80 or above - create seed from FAC1)
+//
+// Output:
+// - FAC1
+//
+// See also:
+// - https://www.atarimagazines.com/compute/issue72/random_numbers.php
+//
+
+rnd_A:
+
+	cmp #$00
+	beq_16 rnd_seed_init
+
+	cmp #$80
+	bcc_16 rnd_generate
+
+	jmp rnd_seed_from_FAC1