Implement RRD/RLD

src/z80_flags.inc.c

@@ -147,6 +147,15 @@ static inline void set_flags_bitshift(Z80 *z80, uint8_t res, uint8_t bit)
 }
 
 /*
+    Set the flags for a RLD or RRD instruction.
+*/
+static inline void set_flags_rd(Z80 *z80)
+{
+    uint8_t a = z80->regs.a;
+    set_flags(z80, 0, 0, PARITY(a), F3(a), 0, F5(a), ZERO(a), SIGN(a), 0xFE);
+}
+
+/*
     Set the flags for a DAA instruction.
 */
 static inline void set_flags_daa(Z80 *z80, uint8_t old, uint8_t adjust)

src/z80_ops.inc.c

@@ -1767,9 +1767,39 @@ static uint8_t z80_inst_srl_hl(Z80 *z80, uint8_t opcode)
     TODO
 */
 
-// TODO: RLD
+/*
+    RLD (0xED6F):
+    Low nibble of (HL) is copied to high nibble of (HL). Old high nibble of
+    (HL) is copied to low nibble of A. Old low nibble of A is copied to low
+    nibble of (HL).
+*/
+static uint8_t z80_inst_rld(Z80 *z80, uint8_t opcode)
+{
+    (void) opcode;
+    uint8_t hl = mmu_read_byte(z80->mmu, z80->regs.hl);
+    uint8_t newhl = (hl << 4) | (z80->regs.a & 0x0F);
+    z80->regs.a = (z80->regs.a & 0xF0) | (hl >> 4);
+    mmu_write_byte(z80->mmu, z80->regs.hl, newhl);
+    set_flags_rd(z80);
+    return 18;
+}
 
-// TODO: RRD
+/*
+    RRD (0xED67):
+    Low nibble of A is copied to high nibble of (HL). Old high nibble of
+    (HL) is copied to low nibble of (HL). Old low nibble of (HL) is copied to
+    low nibble of A.
+*/
+static uint8_t z80_inst_rrd(Z80 *z80, uint8_t opcode)
+{
+    (void) opcode;
+    uint8_t hl = mmu_read_byte(z80->mmu, z80->regs.hl);
+    uint8_t newhl = (z80->regs.a << 4) | (hl >> 4);
+    z80->regs.a = (z80->regs.a & 0xF0) | (hl & 0x0F);
+    mmu_write_byte(z80->mmu, z80->regs.hl, newhl);
+    set_flags_rd(z80);
+    return 18;
+}
 
 /*
     BIT b, r   (0xCB40, 0xCB41, 0xCB42, 0xCB43, 0xCB44, 0xCB45, 0xCB47, 0xCB48,

src/z80_tables.inc.c

@@ -364,7 +364,7 @@ static DispatchTable instruction_table_extended = {
     [0x64] = z80_inst_neg,
     [0x65] = z80_inst_retn,
     [0x66] = z80_inst_im,
-    [0x67] = z80_inst_unimplemented,  // TODO
+    [0x67] = z80_inst_rrd,
     [0x68] = z80_inst_in_r_c,
     [0x69] = z80_inst_out_c_r,
     [0x6A] = z80_inst_adc_hl_ss,
@@ -372,7 +372,7 @@ static DispatchTable instruction_table_extended = {
     [0x6C] = z80_inst_neg,
     [0x6D] = z80_inst_retn,
     [0x6E] = z80_inst_im,
-    [0x6F] = z80_inst_unimplemented,  // TODO
+    [0x6F] = z80_inst_rld,
     [0x70] = z80_inst_in_r_c,
     [0x71] = z80_inst_out_c_r,
     [0x72] = z80_inst_sbc_hl_ss,