The mb86232/86233/86234, also known as the TGP, is used in Sega Model 1, 2 and 2a. There are two, one is used as a T&L unit, the other as a coprocessor. In model 1, both programs are internal to the cpus. In model 2/2a, the T&L program is internal while the coprocessor program is uploaded.

Register numbers are encoded in 3+6 bits. The first 3 bits are some kind of type.

Type 0 and 3 address the same registers. 3 adds a "hi, I'm the destination of the move" twist to it though. Here are the known registers:

Value | Register |
---|---|

00-0f | Register file |

10-12 | a, a.e, a.m |

13-15 | b, b.e, b.m |

16-18 | c, c.e, c.m |

19-1b | d, d.e, d.m |

1c | p |

21 | fifo_in |

22 | fifo_out |

Type 6 looks like special registers. Only value 21 is known as being some kind of indirect access register.

ALU operations are encoded in 6 bits. According to the datasheet the shift operations are not supposed to be there but should be opcodes by themselves.

Value | Type | Operation | Value | Type | Operation | Value | Type | Operation | Value | Type | Operation |
---|---|---|---|---|---|---|---|---|---|---|---|

00 000000 | nop | 10 010000 | f32 | p = a * b | 20 100000 | ? | ? | 30 110000 | int | a = a >> c | |

01 000001 | nop | 11 010001 | f32 | p = a * b | 21 100001 | ? | ? | 31 110001 | int | a = a >> d | |

02 000010 | int | c = c & a | 12 010010 | f32 | c = c + p, p = a * b | 22 100010 | ? | ? | 32 110010 | ? | ? |

03 000011 | int | d = d & a | 13 010011 | f32 | d = d + p, p = a * b | 23 100011 | ? | ? | 33 110011 | ? | ? |

04 000100 | ? | ? | 14 010100 | f32 | c = c - p, p = a * b | 24 100100 | ? | ? | 34 110100 | i24 | c = c + a |

05 000101 | ? | ? | 15 010101 | f32 | d = d - p, p = a * b | 25 100101 | ? | ? | 35 110101 | i24 | d = d + a |

06 000110 | ? | ? | 16 010110 | ? | ? | 26 100110 | ? | ? | 36 110110 | i24 | c = c - a |

07 000111 | ? | ? | 17 010111 | ? | ? | 27 100111 | ? | ? | 37 110111 | i24 | d = d - a |

08 001000 | ? | ? | 18 011000 | f32 | c = a + b | 28 101000 | f32 | c = a - b | 38 111000 | ? | ? |

09 001001 | ? | ? | 19 011001 | f32 | d = a + b | 29 101001 | f32 | d = a - b | 39 111001 | ? | ? |

0a 001010 | ? | ? | 1a 011010 | f32 | c = p, p = a * b | 2a 101010 | ? | ? | 3a 111010 | ? | ? |

0b 001011 | ? | ? | 1b 011011 | f32 | d = p, p = a * b | 2b 101011 | ? | ? | 3b 111011 | ? | ? |

0c 001100 | f32 | c = c + a | 1c 011100 | ? | ? | 2c 101100 | ? | ? | 3c 111100 | ? | ? |

0d 001101 | f32 | d = d + a | 1d 011101 | ? | ? | 2d 101101 | ? | ? | 3d 111101 | ? | ? |

0e 001110 | f32 | c = c - a | 1e 011110 | ? | ? | 2e 101110 | int | a = a << c | 3e 111110 | ? | ? |

0f 001111 | f32 | d = d - a | 1f 011111 | ? | ? | 2f 101111 | int | a = a << d | 3f 111111 | ? | ? |

Known missing: xor, not, neg, abs, comparisons (sub). Operations 36 and 37 (at least) are known to set flags though.

Looks like they may be 3 bits, with 7 meaning 'nop'.