iz80 0.4.4

Z80 and 8080 emulator
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161

use super::opcode::Opcode;
use super::environment::Environment;
use super::registers::{Flag, Reg8};

// Relative jumps
pub fn build_djnz() -> Opcode {
    Opcode::new(
        "DJNZ d".to_string(),
        |env: &mut Environment| {
            let offset = env.advance_pc();
            let b = env.state.reg.get8(Reg8::B).wrapping_add(0xff /* -1 */);
            env.state.reg.set8(Reg8::B, b);
            if b != 0 {
                // Condition not met
                env.set_branch_taken();
                relative_jump(env, offset);
            }
        }
    )
}

pub fn build_jr_unconditional() -> Opcode {
    Opcode::new(
        "JR d".to_string(),
        |env: &mut Environment| {
            let offset = env.advance_pc();
            relative_jump(env, offset);
        }
    )
}

pub fn build_jr_eq((flag, value, name): (Flag, bool, &str)) -> Opcode {
    Opcode::new(
        format!("JR {name}, d"),
        move |env: &mut Environment| {
            let offset = env.advance_pc();
            if env.state.reg.get_flag(flag) == value {
                env.set_branch_taken();
                relative_jump(env, offset);
            }
        }
    )
}


fn relative_jump(env: &mut Environment, offset: u8) {
    let mut pc = env.state.reg.pc();
    pc = pc.wrapping_add(offset as i8 as i16 as u16);
    env.state.reg.set_pc(pc);
}

// Absolute jumps
pub fn build_jp_unconditional() -> Opcode {
    Opcode::new(
        "JP nn".to_string(),
        |env: &mut Environment| {
            let address = env.advance_immediate16();
            env.state.reg.set_pc(address);
        }
    )
}

pub fn build_jp_eq((flag, value, name): (Flag, bool, &str)) -> Opcode {
    Opcode::new(
        format!("JP {name}, nn"),
        move |env: &mut Environment| {
            let address = env.advance_immediate16();
            if env.state.reg.get_flag(flag) == value {
                env.set_branch_taken();
                env.state.reg.set_pc(address);
            }
        }
    )
}

pub fn build_jp_hl() -> Opcode {
    Opcode::new(
        "JP HL".to_string(), // Note: it is usaully written as JP (HL)
        |env: &mut Environment| {
            // Note: no displacement added to the index
            let address = env.index_value();
            env.state.reg.set_pc(address);
        }
    )
}

// Calls to subroutine
pub fn build_call() -> Opcode {
    Opcode::new(
        "CALL nn".to_string(),
        |env: &mut Environment| {
            let address = env.advance_immediate16();
            env.subroutine_call(address);
        }
    )
}

pub fn build_call_eq((flag, value, name): (Flag, bool, &str)) -> Opcode {
    Opcode::new(
        format!("CALL {name}, nn"),
        move |env: &mut Environment| {
            let address = env.advance_immediate16();
            if env.state.reg.get_flag(flag) == value {
                env.set_branch_taken();
                env.subroutine_call(address);
            }
        }
    )
}

pub fn build_rst(d: u8) -> Opcode {
    Opcode::new(
        format!("RST {d:02x}h"),
        move |env: &mut Environment| {
            let address = d as u16;
            env.subroutine_call(address);
        }
    )
}

// Returns

pub fn build_ret() -> Opcode {
    Opcode::new(
        "RET".to_string(),
        |env: &mut Environment| {
            env.subroutine_return();
        }
    )
}

pub fn build_reti() -> Opcode {
    Opcode::new(
        "RETI".to_string(),
        |env: &mut Environment| {
            env.subroutine_return();
        }
    )
}

pub fn build_retn() -> Opcode {
    Opcode::new(
        "RETN".to_string(),
        |env: &mut Environment| {
            env.subroutine_return();
            env.state.reg.end_nmi();
        }
    )
}

pub fn build_ret_eq((flag, value, name): (Flag, bool, &str)) -> Opcode {
    Opcode::new(
        format!("RET {name}"),
        move |env: &mut Environment| {
            if env.state.reg.get_flag(flag) == value {
                env.set_branch_taken();
                env.subroutine_return();
            }
        }
    )
}