megadrive controller port enable?

[dadou]

hi, i would like to know if on the controller port of a megadrive we have a pin "controller_in" or something similiar to "cart_in" which give us if a cartridge is inserted or not

thx you for your answer

[Chilly Willy]

You have to read the port in the "standard" way and look at the results to determine if a controller is inserted or not.

Here's some code that will read 3 or 6 button pads, or return 0xF000 is no pad is found:

| get current pad value
| entry: a0 = pad control port
| exit:  d2 = pad value (0 0 0 1 M X Y Z S A C B R L D U) or (0 0 0 0 0 0 0 0 S A C B R L D U)
get_pad:
        bsr.b   get_input       /* - 0 s a 0 0 d u - 1 c b r l d u */
        move.w  d0,d1
        andi.w  #0x0C00,d0
        bne.b   no_pad
        bsr.b   get_input       /* - 0 s a 0 0 d u - 1 c b r l d u */
        bsr.b   get_input       /* - 0 s a 0 0 0 0 - 1 c b m x y z */
        move.w  d0,d2
        bsr.b   get_input       /* - 0 s a 1 1 1 1 - 1 c b r l d u */
        andi.w  #0x0F00,d0      /* 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 */
        cmpi.w  #0x0F00,d0
        beq.b   common          /* six button pad */
        move.w  #0x010F,d2      /* three button pad */
common:
        lsl.b   #4,d2           /* - 0 s a 0 0 0 0 m x y z 0 0 0 0 */
        lsl.w   #4,d2           /* 0 0 0 0 m x y z 0 0 0 0 0 0 0 0 */
        andi.w  #0x303F,d1      /* 0 0 s a 0 0 0 0 0 0 c b r l d u */
        move.b  d1,d2           /* 0 0 0 0 m x y z 0 0 c b r l d u */
        lsr.w   #6,d1           /* 0 0 0 0 0 0 0 0 s a 0 0 0 0 0 0 */
        or.w    d1,d2           /* 0 0 0 0 m x y z s a c b r l d u */
        eori.w  #0x1FFF,d2      /* 0 0 0 1 M X Y Z S A C B R L D U */
        rts

no_pad:
        move.w  #0xF000,d2
        rts

| read single phase from controller
get_input:
        move.b  #0x00,(a0)
        nop
        nop
        move.b  (a0),d0
        move.b  #0x40,(a0)
        lsl.w   #8,d0
        move.b  (a0),d0
        rts

[dadou]

ok so i don't have a pin like the cart slot, thx you for your answer

[mary123]

hi,
First of all the Megadrive-controller has 9 pins, the Neo Geo Controller has 15 pins. The Megadrive-controller has some coding, it sends serial signals to the console. The Neo Geo has a 1:1 pinout, every button and every direction has it own pin on the controller port, so it's easy to build an own controller for the Neo Geo with standard-arcade-parts.

But you can use the Megadrive-controller on the Atari 2600 and 7800, also on Atari ST, C64, Amiga and every other computer and console that uses the standard-9-pin-layout with only 1 button, also on the Mastersystem. But not on Neo Geo

[fr@ser]

hi,
First of all the Megadrive-controller has 9 pins, the Neo Geo Controller has 15 pins. The Megadrive-controller has some coding, it sends serial signals to the console. The Neo Geo has a 1:1 pinout, every button and every direction has it own pin on the controller port, so it's easy to build an own controller for the Neo Geo with standard-arcade-parts.

But you can use the Megadrive-controller on the Atari 2600 and 7800, also on Atari ST, C64, Amiga and every other computer and console that uses the standard-9-pin-layout with only 1 button, also on the Mastersystem. But not on Neo Geo

It should be easy enough to build a 3 button mega drive pad .All it needs is the 74157 mux IC ,a db9 (male type)and a few high value pullup resistors 10/20K ? The 6 button pad is a different matter though .