Fix a bug in VDP control port writes; rename 'last_index' to 'regs.ixy'.

src/vdp.c

@@ -184,11 +184,13 @@ void vdp_write_control(VDP *vdp, uint8_t byte)
 {
     if (!vdp->control_flag) {  // First byte
         vdp->control_addr = (vdp->control_addr & 0x3F00) + byte;
-    } else {  // Second byte
-        vdp->control_addr = ((byte & 0x3F) << 8) + (vdp->control_addr & 0xFF);
-        vdp->control_code = byte >> 6;
+        vdp->control_flag = true;
+        return;
     }
 
+    vdp->control_addr = ((byte & 0x3F) << 8) + (vdp->control_addr & 0xFF);
+    vdp->control_code = byte >> 6;
+
     if (vdp->control_code == CODE_VRAM_READ) {
         vdp->read_buf = vdp->vram[vdp->control_addr];
         vdp->control_addr = (vdp->control_addr + 1) % 0x3FFF;
@@ -198,7 +200,7 @@ void vdp_write_control(VDP *vdp, uint8_t byte)
             vdp->regs[reg] = vdp->control_addr & 0xFF;
     }
 
-    vdp->control_flag = !vdp->control_flag;
+    vdp->control_flag = false;
 }
 
 /*
@@ -238,6 +240,7 @@ void vdp_write_data(VDP *vdp, uint8_t byte)
 */
 bool vdp_assert_irq(VDP *vdp)
 {
+    // TODO: line interrupts
     return vdp->stat_int && should_frame_interrupt(vdp);
 }
 
@@ -250,6 +253,7 @@ void vdp_dump_registers(const VDP *vdp)
     const uint8_t *regs = vdp->regs;
     DEBUG("Dumping VDP register values:")
 
+    // TODO: show flags
     DEBUG("- $00:  0x%02X (" BINARY_FMT ")", regs[0x00], BINARY_VAL(regs[0]))
     DEBUG("- $01:  0x%02X (" BINARY_FMT ")", regs[0x01], BINARY_VAL(regs[1]))
 

src/z80.c

@@ -60,8 +60,10 @@ void z80_power(Z80 *z80)
     z80->regs.im_a = z80->regs.im_b = 0;
     z80->regs.iff1 = z80->regs.iff2 = 0;
 
+    z80->regs.ixy = NULL;
+    z80->regs.ih = z80->regs.il = NULL;
+
     z80->except = false;
-    z80->last_index = NULL;
     z80->pending_cycles = 0;
 
     z80->trace.fresh = true;
@@ -206,7 +208,7 @@ static inline bool extract_cond(const Z80 *z80, uint8_t opcode)
 */
 static inline uint16_t get_index_addr(Z80 *z80, uint16_t offset_addr)
 {
-    return *z80->last_index + ((int8_t) mmu_read_byte(z80->mmu, offset_addr));
+    return *z80->regs.ixy + ((int8_t) mmu_read_byte(z80->mmu, offset_addr));
 }
 
 /*

src/z80.h

@@ -50,6 +50,9 @@ typedef struct {
     uint8_t  i,  r;
     bool     im_a, im_b;
     bool     iff1, iff2;
+
+    uint16_t *ixy;
+    uint8_t *ih, *il;
 } Z80RegFile;
 
 typedef struct {
@@ -64,7 +67,6 @@ typedef struct {
     IO *io;
     bool except;
     uint8_t exc_code, exc_data;
-    uint16_t *last_index;
     double pending_cycles;
     Z80TraceInfo trace;
 } Z80;

src/z80_ops.inc.c

@@ -246,7 +246,7 @@ static uint8_t z80_inst_ld_dd_nn(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ld_ixy_nn(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    *z80->last_index = mmu_read_double(z80->mmu, ++z80->regs.pc);
+    *z80->regs.ixy = mmu_read_double(z80->mmu, ++z80->regs.pc);
     z80->regs.pc += 2;
     return 14;
 }
@@ -284,7 +284,7 @@ static uint8_t z80_inst_ld_ixy_inn(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
     uint16_t addr = mmu_read_double(z80->mmu, ++z80->regs.pc);
-    *z80->last_index = mmu_read_double(z80->mmu, addr);
+    *z80->regs.ixy = mmu_read_double(z80->mmu, addr);
     z80->regs.pc += 2;
     return 20;
 }
@@ -322,7 +322,7 @@ static uint8_t z80_inst_ld_inn_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
     uint16_t addr = mmu_read_double(z80->mmu, ++z80->regs.pc);
-    mmu_write_double(z80->mmu, addr, *z80->last_index);
+    mmu_write_double(z80->mmu, addr, *z80->regs.ixy);
     z80->regs.pc += 2;
     return 20;
 }
@@ -345,7 +345,7 @@ static uint8_t z80_inst_ld_sp_hl(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ld_sp_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    *z80->last_index = z80->regs.hl;
+    *z80->regs.ixy = z80->regs.hl;
     return 10;
 }
 
@@ -367,7 +367,7 @@ static uint8_t z80_inst_push_qq(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_push_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    stack_push(z80, *z80->last_index);
+    stack_push(z80, *z80->regs.ixy);
     z80->regs.pc++;
     return 15;
 }
@@ -390,7 +390,7 @@ static uint8_t z80_inst_pop_qq(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_pop_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    *z80->last_index = stack_pop(z80);
+    *z80->regs.ixy = stack_pop(z80);
     z80->regs.pc++;
     return 14;
 }
@@ -463,8 +463,8 @@ static uint8_t z80_inst_ex_sp_hl(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_ex_sp_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    uint16_t ixy = *z80->last_index, sp = z80->regs.sp;
-    *z80->last_index = mmu_read_double(z80->mmu, sp);
+    uint16_t ixy = *z80->regs.ixy, sp = z80->regs.sp;
+    *z80->regs.ixy = mmu_read_double(z80->mmu, sp);
     mmu_write_double(z80->mmu, sp, ixy);
     z80->regs.pc++;
     return 23;
@@ -1210,7 +1210,7 @@ static uint8_t z80_inst_jp_hl(Z80 *z80, uint8_t opcode)
 static uint8_t z80_inst_jp_ixy(Z80 *z80, uint8_t opcode)
 {
     (void) opcode;
-    z80->regs.pc = *z80->last_index;
+    z80->regs.pc = *z80->regs.ixy;
     return 8;
 }
 
@@ -1546,7 +1546,16 @@ static uint8_t z80_prefix_bits(Z80 *z80, uint8_t opcode)
 */
 static uint8_t z80_prefix_index(Z80 *z80, uint8_t opcode)
 {
-    z80->last_index = (opcode == 0xDD) ? &z80->regs.ix : &z80->regs.iy;
+    if (opcode == 0xDD) {
+        z80->regs.ixy = &z80->regs.ix;
+        z80->regs.ih  = &z80->regs.ixh;
+        z80->regs.il  = &z80->regs.ixl;
+    } else {
+        z80->regs.ixy = &z80->regs.iy;
+        z80->regs.ih  = &z80->regs.iyh;
+        z80->regs.il  = &z80->regs.iyl;
+    }
+
     opcode = mmu_read_byte(z80->mmu, ++z80->regs.pc);
     return (*instruction_table_index[opcode])(z80, opcode);
 }