nes: add console with cpu bus and step loop

tests: run nestest through nes console

2 files changed, 55 insertions, 0 deletions

diff --git a/nes/bus.go b/nes/bus.go
new file mode 100644
index 0000000..480d178
--- /dev/null
+++ b/nes/bus.go
@@ -0,0 +1,21 @@
+package nes
+
+func (n *Console) Read(addr uint16) uint8 {
+	switch {
+	case addr < 0x2000:
+		return n.RAM[addr&0x7FF]
+	case addr >= 0x4020:
+		return n.Cart.Mapper.CPURead(addr)
+	default:
+		return 0
+	}
+}
+
+func (n *Console) Write(addr uint16, v uint8) {
+	switch {
+    case addr < 0x2000:
+    	n.RAM[addr&0x7FF] = v
+    case addr >= 0x4020:
+    	n.Cart.Mapper.CPUWrite(addr, v)
+    }
+}
\ No newline at end of file
diff --git a/nes/nes.go b/nes/nes.go
new file mode 100644
index 0000000..c4d09a0
--- /dev/null
+++ b/nes/nes.go
@@ -0,0 +1,34 @@
+package nes
+
+import (
+	"crecher.net/gones/v2/cart"
+	"crecher.net/gones/v2/cpu"
+)
+
+type Console struct {
+	CPU *cpu.CPU
+	Cart *cart.Cartridge
+	RAM [0x800]uint8
+	// PPU, APU, controllers once they exist
+	cycles uint64
+}
+
+func New(c *cart.Cartridge) *Console {
+	n := &Console{Cart: c}
+	n.CPU = cpu.NewCPU(n)
+	n.CPU.Reset()
+	return n
+}
+
+func (n *Console) Step() int {
+	cycles := n.CPU.Step()
+	n.cycles += uint64(cycles)
+	return cycles
+}
+
+func (n *Console) StepFrame() {
+	const cyclesPerFrame = 29780 // 29780 ~ 1789773 / 60.1
+	for done := 0; done < cyclesPerFrame; {
+		done += n.Step()
+	}
+}
\ No newline at end of file