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-Parsed / implemented fine addresses for the Intellicart. 

-Implemented the final CRC check.

I didn't get around to implementing bank-switched ranges, but I don't think it's worth worrying about that right now considering that the Intellicart is not marked as readable at the initial PC, so something is either wrong or I need to implement more things before this will work. I think I'll put Intellicarts on hold and try to get a .int / .bin to run in the meantime.
This commit is contained in:
brandman211 2012-07-18 05:35:10 +00:00
parent 188716ab7b
commit 1ee1d03aea
1 changed files with 47 additions and 15 deletions
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62
BizHawk.Emulation/Consoles/Intellivision/Intellicart.cs
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@ -9,6 +9,7 @@ namespace BizHawk.Emulation.Consoles.Intellivision
{ {
private ushort[] Intellicart = new ushort[65536]; private ushort[] Intellicart = new ushort[65536];
private bool[][] MemoryAttributes = new bool[32][]; private bool[][] MemoryAttributes = new bool[32][];
private int[][] FineAddresses = new int[32][];
private ushort[] CRC16_table = private ushort[] CRC16_table =
{ {
@ -51,16 +52,18 @@ namespace BizHawk.Emulation.Consoles.Intellivision
return (ushort)((crc << 8) ^ CRC16_table[(crc >> 8) ^ data]); return (ushort)((crc << 8) ^ CRC16_table[(crc >> 8) ^ data]);
} }
public void Parse() public int Parse()
{ {
int offset = 0; int offset = 0;
// Check to see if the header is valid. // Check to see if the header is valid.
if (Rom[offset++] != 0xA8 || Rom[offset++] != (0xFF ^ Rom[offset++])) if (Rom[offset++] != 0xA8 || Rom[offset++] != (0xFF ^ Rom[offset++]))
throw new ArgumentException(); throw new ArgumentException();
ushort crc;
int expected;
// Parse for data segments. // Parse for data segments.
for (int segment = 0; segment < Rom[1]; segment++) for (int segment = 0; segment < Rom[1]; segment++)
{ {
ushort crc = 0xFFFF; crc = 0xFFFF;
byte upper_start = Rom[offset++]; byte upper_start = Rom[offset++];
byte upper_end = Rom[offset++]; byte upper_end = Rom[offset++];
crc = UpdateCRC16(crc, upper_start); crc = UpdateCRC16(crc, upper_start);
@ -80,43 +83,72 @@ namespace BizHawk.Emulation.Consoles.Intellivision
data = (high << 8) | low; data = (high << 8) | low;
Intellicart[addr] = (ushort)data; Intellicart[addr] = (ushort)data;
} }
int expected = (Rom[offset++] << 8) | Rom[offset++]; expected = (Rom[offset++] << 8) | Rom[offset++];
// Check if there is an invalid CRC. // Check if there is an invalid CRC.
if (expected != crc) if (expected != crc)
throw new ArgumentException(); throw new ArgumentException();
} }
// Parse for memory attributes. // Parse for memory attributes.
for (int attr = 0; attr < 32; attr++) for (int range = 0; range < 32; range++)
{ {
byte attributes = Rom[offset + (attr >> 1)]; byte attributes = Rom[offset + (range >> 1)];
// Every second 2K block is stored in the upper 4 bits. // Every second 2K block is stored in the upper 4 bits.
if ((attr & 0x1) != 0) if ((range & 0x1) != 0)
attributes = (byte)(attributes >> 4); attributes = (byte)(attributes >> 4);
attributes &= 0xF; attributes &= 0xF;
MemoryAttributes[attr] = new bool[4]; MemoryAttributes[range] = new bool[4];
// Readable. // Readable.
MemoryAttributes[attr][0] = ((attr & 0x1) != 0); MemoryAttributes[range][0] = ((range & 0x1) != 0);
// Writeable. // Writeable.
MemoryAttributes[attr][1] = ((attr & 0x2) != 0); MemoryAttributes[range][1] = ((range & 0x2) != 0);
// Narrow. // Narrow.
MemoryAttributes[attr][2] = ((attr & 0x4) != 0); MemoryAttributes[range][2] = ((range & 0x4) != 0);
// Bank-switched. // Bank-switched.
MemoryAttributes[attr][3] = ((attr & 0x8) != 0); MemoryAttributes[range][3] = ((range & 0x8) != 0);
} }
// Parse for fine addresses (Trimmed 2K ranges).
for (int range = 0; range < 32; range++)
{
int index;
// The lower and upper 2K in a 4K range are 16 addresses away from each other.
if ((range & 0x1) != 0)
index = offset + 16 + (range >> 1);
else
index = offset + 32 + (range >> 1);
int range_start = range * 2048;
int start = (((Rom[index] >> 4) & 0x07) << 8) + range_start;
int end = (((Rom[index]) & 0x07) << 8) + 0xFF + range_start;
// This range is invalid if it starts at a higher range than it ends.
if (end < start)
throw new ArgumentException();
FineAddresses[range] = new int[2];
FineAddresses[range][0] = start;
FineAddresses[range][1] = end;
}
crc = 0xFFFF;
for (int index = 0; index < 48; index++)
crc = UpdateCRC16(crc, Rom[offset++]);
expected = (Rom[offset++] << 8) | (Rom[offset++] & 0xFF);
// Check if there is an invalid CRC for the memory attributes / fine addresses.
if (expected != crc)
throw new ArgumentException();
return offset;
} }
public ushort? ReadCart(ushort addr) public ushort? ReadCart(ushort addr)
{ {
bool[] attributes = MemoryAttributes[addr / 2048]; int range = addr / 2048;
if (attributes[0]) bool[] attributes = MemoryAttributes[range];
if (attributes[0] && addr >= FineAddresses[range][0] && addr <= FineAddresses[range][1])
return Intellicart[addr]; return Intellicart[addr];
return null; return null;
} }
public bool WriteCart(ushort addr, ushort value) public bool WriteCart(ushort addr, ushort value)
{ {
bool[] attributes = MemoryAttributes[addr / 2048]; int range = addr / 2048;
if (attributes[1]) bool[] attributes = MemoryAttributes[range];
if (attributes[1] && addr >= FineAddresses[range][0] && addr <= FineAddresses[range][1])
{ {
// Only write lower 8 bits if the Narrow attribute is set. // Only write lower 8 bits if the Narrow attribute is set.
if (attributes[2]) if (attributes[2])