Added C64 Chameleon accelerator code and documentation.

libsrc/c64/acc_detect_chameleon.s

@@ -0,0 +1,39 @@
+;
+; Marco van den Heuvel, 2018-04-25
+;
+
+; unsigned char detect_chameleon (void);
+;
+;/* Check for the presence of the Chameleon cartridge.
+; *
+; * Possible return values:
+; * 0x00  : Chameleon cartridge not present
+; * 0x01  : Chameleon cartridge present
+; */
+
+        .export         _detect_chameleon
+
+        .include        "accelerator.inc"
+
+_detect_chameleon:
+        lda     #$00
+        tax
+
+; Make sure the CPU is a 6510
+        .byte   $1A                   ; NOP on 6510, INA on 65(S)C(E)02, 4510 and 65816
+        bne     not_found
+
+        ldy     CHAMELEON_CFGENA
+        lda     #CHAMELEON_ENABLE_REGS
+        sta     CHAMELEON_CFGENA
+        lda     CHAMELEON_CFGENA
+        sty     CHAMELEON_CFGENA
+        cmp     #$FF
+        beq     not_found
+found:
+        lda     #$01
+        .byte   $2C
+not_found:
+        lda     #$00
+        rts
+