Z80 wait instructions
From MSX Game Library
Z80 instruction set that don't change registers value (except for F register):
| Inst. | T-S | Bytes | Flag modification |
|---|---|---|---|
| NOP | 5 | 1 | None |
| CP (HL) | 8 | 1 | C, S, and Z flags modified by definition. P/V detects overflow. |
| NOP NOP |
10 | 2 | None |
| SCF RET NC |
11 | 2 | Carry flag set, H and N cleared, rest are preserved. |
| JR $+2 | 13 | 2 | None |
| BIT 0,(HL) | 14 | 2 | Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined. |
| NOP NOP NOP |
15 | 3 | None |
| CP (HL) CP (HL) |
16 | 2 | C, S, and Z flags modified by definition. P/V detects overflow. |
| SCF RET NC RET NC |
17 | 3 | Carry flag set, H and N cleared, rest are preserved. |
| NOP NOP CP (HL) |
18 | 3 | C, S, and Z flags modified by definition. P/V detects overflow. |
| NOP BIT 0,(HL) |
19 | 3 | Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined. |
| NOP NOP NOP NOP |
20 | 4 | None |
| CP (IY+0) | 21 | 3 | C, S, and Z flags modified by definition. P/V detects overflow. |
| CP (HL) BIT 0,(HL) |
22 | 3 | C, S, and Z flags modified by definition. P/V detects overflow. Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined. |
| PUSH AF POP AF |
23 | 2 | None |
| CP (HL) CP (HL) CP (HL) |
24 | 3 | C, S, and Z flags modified by definition. P/V detects overflow. |
| INC (HL) DEC (HL) |
24 | 2 | Preserves C flag, N flag is reset, P/V detects overflow and rest are modified by definition. C flag preserved, P/V detects overflow and rest modified by definition. ⚠️ Not interrupt safe |
| NOP NOP NOP NOP NOP |
25 | 5 | None |
| NOP CP (IY+0) |
26 | 4 | C, S, and Z flags modified by definition. P/V detects overflow. |
| NOP CP (HL) BIT 0,(HL) |
27 | 4 | C, S, and Z flags modified by definition. P/V detects overflow. Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined. |
| NOP PUSH AF POP AF |
28 | 3 | None |
| CP (IY+0) CP (HL) |
29 | 4 | C, S, and Z flags modified by definition. P/V detects overflow. |
| NOP INC (HL) DEC (HL) |
29 | 3 | Preserves C flag, N flag is reset, P/V detects overflow and rest are modified by definition. C flag preserved, P/V detects overflow and rest modified by definition. ⚠️ Not interrupt safe |
| BIT 0,(HL) CP (HL) CP (HL) |
30 | 4 | Opposite of the bit #0 is written into the Z flag. C is preserved, N is reset, H is set, and S and P/V are undefined. C, S, and Z flags modified by definition. P/V detects overflow. |