84 lines
3.2 KiB
C#
84 lines
3.2 KiB
C#
using System.Diagnostics;
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using Core.Interfaces;
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using Core.Memory;
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using static System.Runtime.InteropServices.JavaScript.JSType;
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namespace Core.Io
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{
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public class IO_Bus
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{
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public byte BorderColourIndex { get; set; } = 7;
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public byte KempstonState { get; set; } = 0x00;
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public bool BeeperState { get; private set; } = false;
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public byte[] KeyboardRows = new byte[8] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
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TapManager _tapManager = new TapManager();
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MemoryBus _memory;
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public IO_Bus(TapManager tapManager, MemoryBus memoryBus)
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{
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_tapManager = tapManager;
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_memory = memoryBus;
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}
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public byte ReadPort(ushort portAddress)
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{
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//ULA responds to any even port address (where the lowest bit is 0)
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if ((portAddress & 0x01) == 0) //Port 0xFE)
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{
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byte highByte = (byte)(portAddress >> 8); // The B register
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byte result = 0xFF; // Start assuming no keys are pressed
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if ((highByte & 0x01) == 0) result &= KeyboardRows[0]; // 0xFE: CAPS, Z, X, C, V
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if ((highByte & 0x02) == 0) result &= KeyboardRows[1]; // 0xFD: A, S, D, F, G
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if ((highByte & 0x04) == 0) result &= KeyboardRows[2]; // 0xFB: Q, W, E, R, T
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if ((highByte & 0x08) == 0) result &= KeyboardRows[3]; // 0xF7: 1, 2, 3, 4, 5
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if ((highByte & 0x10) == 0) result &= KeyboardRows[4]; // 0xEF: 0, 9, 8, 7, 6
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if ((highByte & 0x20) == 0) result &= KeyboardRows[5]; // 0xDF: P, O, I, U, Y
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if ((highByte & 0x40) == 0) result &= KeyboardRows[6]; // 0xBF: ENTER, L, K, J, H
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if ((highByte & 0x80) == 0) result &= KeyboardRows[7]; // 0x7F: SPACE, SYM, M, N, B
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if (_tapManager.EarBit) result |= 0x40; // Set Bit 6 high
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else result &= 0xBF; // Set Bit 6 low
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//The top 3 bits (5, 6, 7) are unused by the keyboard and usually return 1 on a real Spectrum
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return (byte)(result | 0xA0);
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}
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//Kempston Joystick Port
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if ((portAddress & 0xFF) == 0x1F)
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{
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return KempstonState;
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}
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//Return 0xFF for unhandled ports
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return 0x00;
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}
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public void WritePort(ushort portAddress, byte portValue)
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{
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// The ULA intercepts any write to an even port address
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if ((portAddress & 0x01) == 0)
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{
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// The bottom 3 bits (0-2) define the border color
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BorderColourIndex = (byte)(portValue & 0x07);
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// Bit 4 controls the speaker
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BeeperState = (portValue & 0x10) != 0;
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// Bit 3 handles the cassette MIC output
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}
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// 128K Standard Paging Port (0x7FFD)
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if ((portAddress & 0x8002) == 0)
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{
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_memory.HandlePaging(0x7FFD, portValue);
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}
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// +2A/+3 Extended Paging Port (0x1FFD)
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if ((portAddress & 0xF002) == 0x1000)
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{
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_memory.HandlePaging(0x1FFD, portValue);
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}
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}
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}
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} |