--- a/debug.c	Sat Oct 28 16:04:58 2023 -0700
+++ b/debug.c	Mon Oct 30 00:07:56 2023 -0700
@@ -45,10 +45,10 @@
 	return NULL;
 }
 
-bp_def ** find_breakpoint(bp_def ** cur, uint32_t address)
+bp_def ** find_breakpoint(bp_def ** cur, uint32_t address, uint8_t type)
 {
 	while (*cur) {
-		if ((*cur)->address == address) {
+		if ((*cur)->type == type && (*cur)->address == (((*cur)->mask) & address)) {
 			break;
 		}
 		cur = &((*cur)->next);
@@ -2192,7 +2192,9 @@
 		return 1;
 	}
 	bp_def *tmp = *this_bp;
-	remove_breakpoint(root->cpu_context, tmp->address);
+	if (tmp->type == BP_TYPE_CPU) {
+		remove_breakpoint(root->cpu_context, tmp->address);
+	}
 	*this_bp = (*this_bp)->next;
 	if (tmp->commands) {
 		for (uint32_t i = 0; i < tmp->num_commands; i++)
@@ -2211,12 +2213,72 @@
 	bp_def *new_bp = calloc(1, sizeof(bp_def));
 	new_bp->next = root->breakpoints;
 	new_bp->address = cmd->args[0].value;
+	new_bp->mask = 0xFFFFFF;
 	new_bp->index = root->bp_index++;
+	new_bp->type = BP_TYPE_CPU;
 	root->breakpoints = new_bp;
 	printf("68K Breakpoint %d set at %X\n", new_bp->index, cmd->args[0].value);
 	return 1;
 }
 
+static void on_vdp_reg_write(vdp_context *context, uint16_t reg, uint16_t value)
+{
+	value &= 0xFF;
+	if (context->regs[reg] == value) {
+		return;
+	}
+	genesis_context *gen = (genesis_context *)context->system;
+	debug_root *root = find_m68k_root(gen->m68k);
+	bp_def **this_bp = find_breakpoint(&root->breakpoints, reg, BP_TYPE_VDPREG);
+	int debugging = 1;
+	if (*this_bp) {
+		if ((*this_bp)->condition) {
+			uint32_t condres;
+			if (eval_expr(root, (*this_bp)->condition, &condres)) {
+				if (!condres) {
+					return;
+				}
+			} else {
+				fprintf(stderr, "Failed to eval condition for VDP Register Breakpoint %u\n", (*this_bp)->index);
+				free_expr((*this_bp)->condition);
+				(*this_bp)->condition = NULL;
+			}
+		}
+		for (uint32_t i = 0; debugging && i < (*this_bp)->num_commands; i++)
+		{
+			debugging = run_command(root, (*this_bp)->commands + i);
+		}
+		if (debugging) {
+			printf("VDP Register Breakpoint %d hit on register write %X - Old: %X, New: %X\n", (*this_bp)->index, reg, context->regs[reg], value);
+			gen->header.enter_debugger = 1;
+			if (gen->m68k->sync_cycle > gen->m68k->current_cycle + 1) {
+				gen->m68k->sync_cycle = gen->m68k->current_cycle + 1;
+			}
+			if (gen->m68k->target_cycle > gen->m68k->sync_cycle) {
+				gen->m68k->target_cycle = gen->m68k->sync_cycle;
+			}
+		}
+	}
+}
+
+static uint8_t cmd_vdp_reg_break(debug_root *root, parsed_command *cmd)
+{
+	bp_def *new_bp = calloc(1, sizeof(bp_def));
+	new_bp->next = root->breakpoints;
+	if (cmd->num_args) {
+		new_bp->address = cmd->args[0].value;
+		new_bp->mask = cmd->num_args > 1 ? cmd->args[1].value : 0xFF;
+	}
+	new_bp->index = root->bp_index++;
+	new_bp->type = BP_TYPE_VDPREG;
+	root->breakpoints = new_bp;
+	m68k_context *m68k = root->cpu_context;
+	genesis_context *gen = m68k->system;
+	gen->vdp->reg_hook = on_vdp_reg_write;
+	printf("VDP Register Breakpoint %d set\n", new_bp->index);
+	return 1;
+}
+
 static uint8_t cmd_advance_m68k(debug_root *root, parsed_command *cmd)
 {
 	insert_breakpoint(root->cpu_context, cmd->args[0].value, debugger);
@@ -2817,7 +2879,7 @@
 	},
 	{
 		.names = (const char *[]){
-			"vdpsregs", "vr", NULL
+			"vdpregs", "vr", NULL
 		},
 		.usage = "vdpregs",
 		.desc = "Print VDP register values with a short description",
@@ -2825,6 +2887,16 @@
 		.min_args = 0,
 		.max_args = 0
 	},
+	{
+		.names = (const char *[]){
+			"vdpregbreak", "vregbreak", "vrb", NULL
+		},
+		.usage = "vdpregbreak [REGISTER [MASK]]",
+		.desc = "Enter debugger on VDP register write. If REGISTER is provided, breakpoint will only fire for writes to that register. If MASK is also provided, it will be applied to the register number before comparison with REGISTER",
+		.impl = cmd_vdp_reg_break,
+		.min_args = 0,
+		.max_args = 2
+	},
 #ifndef NO_Z80
 	{
 		.names = (const char *[]){
@@ -2923,6 +2995,8 @@
 	bp_def *new_bp = calloc(1, sizeof(bp_def));
 	new_bp->next = root->breakpoints;
 	new_bp->address = cmd->args[0].value;
+	new_bp->mask = 0xFFFF;
+	new_bp->type = BP_TYPE_CPU;
 	new_bp->index = root->bp_index++;
 	root->breakpoints = new_bp;
 	printf("Z80 Breakpoint %d set at %X\n", new_bp->index, cmd->args[0].value);
@@ -3829,7 +3903,7 @@
 	}
 	root->address = address;
 	//Check if this is a user set breakpoint, or just a temporary one
-	bp_def ** this_bp = find_breakpoint(&root->breakpoints, address);
+	bp_def ** this_bp = find_breakpoint(&root->breakpoints, address, BP_TYPE_CPU);
 	if (*this_bp) {
 		if ((*this_bp)->condition) {
 			uint32_t condres;
@@ -3902,13 +3976,13 @@
 	//probably not necessary, but let's play it safe
 	address &= 0xFFFFFF;
 	if (address == root->branch_t) {
-		bp_def ** f_bp = find_breakpoint(&root->breakpoints, root->branch_f);
+		bp_def ** f_bp = find_breakpoint(&root->breakpoints, root->branch_f, BP_TYPE_CPU);
 		if (!*f_bp) {
 			remove_breakpoint(context, root->branch_f);
 		}
 		root->branch_t = root->branch_f = 0;
 	} else if(address == root->branch_f) {
-		bp_def ** t_bp = find_breakpoint(&root->breakpoints, root->branch_t);
+		bp_def ** t_bp = find_breakpoint(&root->breakpoints, root->branch_t, BP_TYPE_CPU);
 		if (!*t_bp) {
 			remove_breakpoint(context, root->branch_t);
 		}
@@ -3918,7 +3992,7 @@
 	root->address = address;
 	int debugging = 1;
 	//Check if this is a user set breakpoint, or just a temporary one
-	bp_def ** this_bp = find_breakpoint(&root->breakpoints, address);
+	bp_def ** this_bp = find_breakpoint(&root->breakpoints, address, BP_TYPE_CPU);
 	if (*this_bp) {
 		if ((*this_bp)->condition) {
 			uint32_t condres;