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Implementing DEC

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This commit is contained in:
Anonymus Raccoon
2020-04-06 18:05:00 +02:00
parent 5ded0b44e8
commit f675e45385
3 changed files with 113 additions and 5 deletions
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sources/CPU/CPU.hpp
+7 -5
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@@ -393,6 +393,8 @@ namespace ComSquare::CPU
int CMP(uint24_t, AddressingMode);
//! @brief Increment
int INC(uint24_t, AddressingMode);
//! @brief Decrement
int DEC(uint24_t, AddressingMode);
//! @brief All the instructions of the CPU.
//! @info Instructions are indexed by their opcode
@@ -455,7 +457,7 @@ namespace ComSquare::CPU
{&CPU::AND, 6, "and", AddressingMode::DirectPageIndirectIndexedByYLong, 2}, // 37
{&CPU::SEC, 2, "sec", AddressingMode::Implied, 1}, // 38
{&CPU::AND, 4, "and", AddressingMode::AbsoluteIndexedByY, 3}, // 39
{&CPU::BRK, 7, "dec #-#", AddressingMode::Implied, 2}, // 3A
{&CPU::DEC, 2, "dec", AddressingMode::Implied, 1}, // 3A
{&CPU::BRK, 7, "tsc #-#", AddressingMode::Implied, 2}, // 3B
{&CPU::BRK, 7, "bit #-#", AddressingMode::Implied, 2}, // 3C
{&CPU::AND, 4, "and", AddressingMode::AbsoluteIndexedByX, 3}, // 3D
@@ -595,7 +597,7 @@ namespace ComSquare::CPU
{&CPU::CMP, 4, "cmp", AddressingMode::StackRelative, 2}, // C3
{&CPU::CPY, 3, "cpy", AddressingMode::DirectPage, 2}, // C4
{&CPU::CMP, 3, "cmp", AddressingMode::DirectPage, 2}, // C5
{&CPU::BRK, 7, "dec #-#", AddressingMode::Implied, 2}, // C6
{&CPU::DEC, 5, "dec", AddressingMode::DirectPage, 2}, // C6
{&CPU::CMP, 6, "cmp", AddressingMode::DirectPageIndirectLong, 2}, // C7
{&CPU::INY, 2, "iny", AddressingMode::Implied, 1}, // C8
{&CPU::CMP, 2, "cmp", AddressingMode::ImmediateForA, 2}, // C9
@@ -603,7 +605,7 @@ namespace ComSquare::CPU
{&CPU::BRK, 7, "wai #-#", AddressingMode::Implied, 2}, // CB
{&CPU::CPY, 4, "cpy", AddressingMode::Absolute, 3}, // CC
{&CPU::CMP, 4, "cmp", AddressingMode::Absolute, 3}, // CD
{&CPU::BRK, 7, "dec #-#", AddressingMode::Implied, 2}, // CE
{&CPU::DEC, 6, "dec", AddressingMode::Absolute, 3}, // CE
{&CPU::CMP, 6, "cmp", AddressingMode::AbsoluteLong, 4}, // CF
{&CPU::BNE, 2, "bne", AddressingMode::Implied, 2}, // D0
{&CPU::CMP, 5, "cmp", AddressingMode::DirectPageIndirectIndexedByY, 2}, // D1
@@ -611,7 +613,7 @@ namespace ComSquare::CPU
{&CPU::CMP, 7, "cmp", AddressingMode::StackRelativeIndirectIndexedByY, 2}, // D3
{&CPU::BRK, 7, "pei #-#", AddressingMode::Implied, 2}, // D4
{&CPU::CMP, 4, "cmp", AddressingMode::DirectPageIndexedByX, 2}, // D5
{&CPU::BRK, 7, "dec #-#", AddressingMode::Implied, 2}, // D6
{&CPU::DEC, 6, "dec", AddressingMode::DirectPageIndexedByX, 2}, // D6
{&CPU::CMP, 6, "cmp", AddressingMode::DirectPageIndirectIndexedByYLong, 2}, // D7
{&CPU::CLD, 2, "cld", AddressingMode::Implied, 2}, // D8
{&CPU::CMP, 4, "cmp", AddressingMode::AbsoluteIndexedByY, 3}, // D9
@@ -619,7 +621,7 @@ namespace ComSquare::CPU
{&CPU::BRK, 7, "stp #-#", AddressingMode::Implied, 2}, // DB
{&CPU::JML, 7, "jml", AddressingMode::AbsoluteIndirectLong, 2}, // DC
{&CPU::CMP, 4, "cmp", AddressingMode::AbsoluteIndexedByX, 3}, // DD
{&CPU::BRK, 7, "dec #-#", AddressingMode::Implied, 2}, // DE
{&CPU::DEC, 7, "dec", AddressingMode::AbsoluteIndexedByX, 3}, // DE
{&CPU::CMP, 5, "cmp", AddressingMode::AbsoluteIndexedByXLong, 4}, // DF
{&CPU::CPX, 2, "cpx", AddressingMode::ImmediateForX, 2}, // E0
{&CPU::SBC, 6, "sbc", AddressingMode::DirectPageIndirectIndexedByX, 2}, // E1
sources/CPU/Instructions/MathematicalOperations.cpp
+40
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@@ -325,4 +325,44 @@ namespace ComSquare::CPU
return 0;
}
}
int CPU::DEC(uint24_t valueAddr, AddressingMode mode)
{
unsigned negativeMask = this->_registers.p.m ? 0x80u : 0x8000u;
unsigned result;
if (mode == Implied) {
this->_registers.a--;
if (this->_registers.p.m)
this->_registers.ah = 0;
result = this->_registers.a;
} else if (!this->_registers.p.m) {
result = this->_bus->read(valueAddr);
result += this->_bus->read(valueAddr + 1) << 8u;
result = (uint16_t)(result - 1);
this->_bus->write(valueAddr, result);
this->_bus->write(valueAddr + 1, result << 8u);
} else {
result = this->_bus->read(valueAddr);
result = (uint8_t)(result - 1);
this->_bus->write(valueAddr, result);
}
this->_registers.p.z = result == 0;
this->_registers.p.n = result & negativeMask;
switch (mode) {
case Implied:
return 0;
case Absolute:
return this->_registers.p.m == 0 ? 2 : 0;
case DirectPage:
case DirectPageIndexedByX:
return (this->_registers.p.m == 0 ? 2 : 0) + this->_registers.dl != 0 ;
case AbsoluteIndexedByX:
return (this->_registers.p.m == 0 ? 2 : 0) + this->_hasIndexCrossedPageBoundary;
default:
return 0;
}
}
}