dragon-nx-32: add some minimal MPI helpers

Makes it much easier to do dev work if we can have several carts loaded!

diff --git a/Kernel/platform-dragon-nx32/dragon.s b/Kernel/platform-dragon-nx32/dragon.s
index c804aa9..94d343b 100644 (file)
--- a/Kernel/platform-dragon-nx32/dragon.s
+++ b/Kernel/platform-dragon-nx32/dragon.s
@@ -5,6 +5,9 @@
                .module dragon
 
                ; exported
+               .globl _mpi_present
+               .globl _mpi_set_slot
+               .globl _cart_hash
 
                ; imported
                .globl unix_syscall_entry
@@ -109,24 +112,73 @@ _program_vectors:
            rts
 
 ;
+;      Helpers for the MPI and Cartridge Detect
+;
+
+;
+;      oldslot = mpi_set_slot(uint8_t newslot)
+;
+_mpi_set_slot:
+       tfr b,a
+       ldb 0xff7f
+       sta 0xff7f
+       rts
+;
+;      int8_t mpi_present(void)
+;
+_mpi_present:
+       lda 0xff7f      ; Save bits
+       ldb #0xff       ; Will get back 33 from an MPI cartridge
+       stb 0xff7f      ; if the emulator is right on this
+       ldb 0xff7f
+       cmpb #0x33
+       bne nompi
+       clr 0xff7f      ; Switch to slot 0
+       ldb 0xff7f
+       bne nompi
+       incb
+       sta 0xff7f      ; Our becker port for debug will be on the default
+                       ; slot so put it back for now
+       rts             ; B = 0
+nompi: ldb #0
+       sta 0xff7f      ; Restore bits just in case
+       rts
+
+;
+;      uint16_t cart_hash(void)
+;
+_cart_hash:
+       pshs cc
+       orcc #0x10
+       ldx #0xC000
+       ldd #0
+       clr $FFBE       ; Map cartridge
+hashl:
+       addd ,x++
+       cmpx #0xC200
+       bne hashl
+       tfr d,x
+       clr $FFBF       ; Return to normality
+       puls cc,pc
+;
 ;      FIXME:
 ;
 firq_handler:
 badswi_handler:
            rti
 
-; outchar: Simple writing to video memory
-; FIXME: bank switching ???
+;
+;      debug via printer port
+;
 outchar:
-           pshs x,d,pc
-           sta outbuf
-           ldx #outbuf
-           lda #1
-           pshs a
-           jsr _vtoutput
-           puls x,d,pc
+           sta 0xFF02
+           lda 0xFF20
+           ora #0x02
+           sta 0xFF20
+           anda #0xFD
+           sta 0xFF20
+           rts
 
            .area .common
 
-outbuf:            .db 0
 _need_resched: .db 0