More flexible bus system that takes VIC-20 address mapping and multiplexed buses like the MCS-4 into account.

Broken currently, subject to fixes

src/components/memory/intel_4001.rs

@@ -0,0 +1,56 @@
+use crate::components::memory::generic_rom::GenericRom;
+use crate::{Component, PinValue};
+use crate::systems::intel_mcs_4::MCS4Phase;
+
+// 4001 ROM: 256 bytes, 4-bit data width
+pub type Intel4001 = GenericRom<256, 4>;
+impl Intel4001 {
+    fn update(&mut self) -> Result<(), String> {
+        // Read the current bus phase from the pins
+        let phase = self.detect_bus_phase();
+
+        match phase {
+            MCS4Phase::AddressLow => {
+                self.latch_address_low();
+            }
+            MCS4Phase::AddressHigh => {
+                self.latch_address_high();
+                if self.is_selected() {
+                    self.prepare_data_output();
+                }
+            }
+            MCS4Phase::DataRead => {
+                if self.is_selected() {
+                    self.output_data();
+                }
+            }
+            _ => {
+                // Put pins in high impedance
+                self.set_pins_high_z();
+            }
+        }
+
+        Ok(())
+    }
+    fn detect_bus_phase(&self) -> MCS4Phase {
+        // Detect phase based on sync and other control signals
+        if let Some(sync_pin) = self.base.get_pin("pin_0") {
+            match sync_pin.read() {
+                PinValue::High => MCS4Phase::AddressLow, // Sync high = address phase
+                PinValue::Low => MCS4Phase::DataRead,    // Sync low = data phase
+                _ => MCS4Phase::AddressLow,
+            }
+        } else {
+            MCS4Phase::AddressLow
+        }
+    }
+    fn latch_address_low(&mut self) {
+        let addr_low = self.read_nibble_from_pins(9..12);
+        self.latched_address = (self.latched_address & 0xFF0) | (addr_low as u16);
+    }
+    fn latch_address_high(&mut self) {
+        let addr_high = self.read_nibble_from_pins(9..12);
+        let addr_mid = self.read_nibble_from_pins(13..16);
+        self.latched_address = ((addr_mid as u16) << 8) | ((addr_high as u16) << 4) | (self.latched_address & 0x00F);
+    }
+}