wip ppu

1 files changed, 21 insertions, 0 deletions

diff --git a/src/nes/cpu.cc b/src/nes/cpu.cc
index 9b5ed66..bb4830f 100644
--- a/src/nes/cpu.cc
+++ b/src/nes/cpu.cc
@@ -38,6 +38,11 @@ namespace nes
 		current_cycles_ += count;
 	}
 
+	auto cpu::trigger_nmi() -> void
+	{
+		nmi_pending_ = true;
+	}
+
 	auto cpu::step_to(cycle_count const target) -> void
 	{
 		while (current_cycles_ < target)
@@ -50,6 +55,12 @@ namespace nes
 	{
 		// See https://www.nesdev.org/wiki/CPU_unofficial_opcodes
 
+		if (nmi_pending_)
+		{
+			execute_interrupt(address{ 0xFFFA });
+			nmi_pending_ = false;
+		}
+
 		auto const opcode = advance_pc8();
 		switch (opcode)
 		{
@@ -1035,6 +1046,16 @@ namespace nes
 		}
 	}
 
+	auto cpu::execute_interrupt(address vector) -> void
+	{
+		push_stack16(registers_.pc);
+		run_php();
+		registers_.pc = read16(vector);
+		registers_.i = true;
+		current_cycles_ += cycle_count::from_cpu(7);
+	}
+
+
 	auto cpu::eval_ror(std::uint8_t const arg) -> std::uint8_t
 	{
 		auto const res = static_cast<std::uint8_t>((registers_.c << 7) | (arg >> 1));