Created a target and a library for the Commander X16 prototype computer.

libsrc/cx16/bordercolor.s

@@ -0,0 +1,27 @@
+;
+; 2019-09-23, Greg King
+;
+; unsigned char __fastcall__ bordercolor (unsigned char color);
+; /* Set the color for the border. The old color setting is returned. */
+;
+
+        .export         _bordercolor
+
+        .include        "cx16.inc"
+
+_bordercolor:
+        tax
+
+        ; Point to the border color register.
+
+        stz     VERA::CTRL              ; Use port 0
+        lda     #<VERA::COMPOSER::FRAME
+        sta     VERA::ADDR
+        lda     #>VERA::COMPOSER::FRAME
+        sta     VERA::ADDR+1
+        ldy     #^VERA::COMPOSER::FRAME | VERA::INC0
+        sty     VERA::ADDR+2
+
+        lda     VERA::DATA0             ; get old value
+        stx     VERA::DATA0             ; set new value
+        rts