Added c64dtv accelerator code and documentation.

2018-04-14 10:40:13 -07:00
parent a10f36c837
commit 6076316f38
8 changed files with 238 additions and 3 deletions
--- a/libsrc/c64/acc_detect_c64dtv.s
+++ b/libsrc/c64/acc_detect_c64dtv.s
@@ -0,0 +1,43 @@
+;
+; Marco van den Heuvel, 2018-04-14
+;
+
+; unsigned char detect_c64dtv (void);
+;
+;/* Check for the presence of the C64DTV.
+; *
+; * Possible return values:
+; * 0x00  : C64DTV not present
+; * 0x01  : C64DTV present
+; */
+
+        .export         _detect_c64dtv
+
+        .include        "accelerator.inc"
+
+_detect_c64dtv:
+        ldy     C64DTV_Extended_Regs
+        lda     #$00
+        tax
+
+; Make sure the CPU is a 6510
+        .byte   $1A                   ; NOP on 8502, INA on 65(S)C(E)02, 4510 and 65816
+        bne     not_found
+        lda     #$01
+        sta     C64DTV_Extended_Regs
+
+; Check if $D000 is mirrored at $D040
+        lda     $D040
+        cmp     $D000
+        bne     found
+        inc     $D040
+        cmp     $D000
+        bne     not_found
+found:
+        lda     #$01
+        .byte   $2C
+not_found:
+        lda     #$00
+        sty     C64DTV_Extended_Regs
+        rts
+