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MiST Derivatives

The MiST firmware was derived from Minimig, but it has served as the basis for other systems:

  • SiDi, shares the same MCU and binary firmware
  • NeptUNO, comes from Multicore, which seems to be influenced by MiST

Some systems use a different file extension for the RBF

System RBF file extension
MiST, SiDi rbf
Neptuno np1
Multicore 2+ mcp
Multicore 2 mc2

NeptUNO

This system has a primitive I/O and disk management:

  • Only direct PS2 and DB9 inputs connected to the FPGA
  • The RBF must be renamed to .NP1
  • The ROM file must be called like the core file, with the .DAT extension
  • The ROM file must be specified in the config string like P,myrom.dat but it can also use the format P,CORE_NAME.dat and that will match the .dat file with the same name as the .np1
  • ARC files are not allowed, a syntax subset seems supported in the form of INI files
  • The firmware won't send the ROM file to the core unless the core requests it. The module pump signal seems to serve this purpose

The firmware can ask for commands to the core, by sending the code $14, then the code can reply with a byte with the format CCCKKKKK

CCC is the "command":

Bits 7:5 Use
111 Read keyboard input
001 Pump ROM (parameter "p")
011 OSD Menu (usually F12 key)

The pump command will be executed by loading the file pointed by P,...dat in the config string.

KKKKK encodes the keyboard and joystick inputs. The source code documents the following values (in decimal):

#define KEY_UP  30
#define KEY_DOW 29
#define KEY_LFT 27
#define KEY_RGT 23
#define KEY_RET 15
#define KEY_NOTHING 31
#define KEY_A   0
#define KEY_B   1
#define KEY_C   2
#define KEY_D   3
#define KEY_E   4
#define KEY_F   5
#define KEY_G   6
#define KEY_H   7
#define KEY_I   8
#define KEY_J   9
#define KEY_K   10
#define KEY_L   11
#define KEY_M   12
#define KEY_N   13
#define KEY_O   14
#define KEY_P   16
#define KEY_Q   17
#define KEY_R   18
#define KEY_S   19
#define KEY_T   20
#define KEY_U   21
#define KEY_V   22
#define KEY_W   24
#define KEY_X   25
#define KEY_Y   26
#define KEY_Z   28

A sample I/O code can be seen here.

NeptUNO has a 2MB SRAM module too, which JTFRAME does not support.

Gamepad Button Assignments

[../hdl/neptuno/jtframe_neptuno_io.v](The Neptuno I/O) module expects a Megadrive DB9 controller to work. Special inputs:

Buttons Use
Start+C Display, hide OSD
A Functions as enter in the OSD
Start+B Press during 2 seconds to toggle the scan doubler*
  • Not implemented yet

Multicore 2(+)

The MC2 and MC2+ platforms have four buttons, whose functions are expected to be:

Button OSD Arcade
0 up 1P
1 enter 2P
2 down coin
3 open/close Hold for reset

The arcade functions are not supported.