6502/CLK
1
0
Fork 0
mirror of https://github.com/TomHarte/CLK.git synced 2025-11-05 06:16:26 +00:00
Code Issues Projects Releases Wiki Activity

Add extra cycle to immediate decimal arithmetic.

Browse Source
This commit is contained in:
Thomas Harte
2025-10-24 21:39:14 -04:00
parent 76a5872d17
commit fe79a1231d
1 changed files with 23 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
Processors/6502Mk2/Implementation/6502.hpp
View File

@@ -76,6 +76,14 @@ void Processor<model, Traits>::run_for(const Cycles cycles) {
Storage::opcode_ Storage::opcode_
); );
}; };
const auto needs_65c02_extra_arithmetic_cycle = [&] {
return
is_65c02(model) &&
(
Storage::decoded_.operation == Operation::ADC ||
Storage::decoded_.operation == Operation::SBC
) && registers.flags.decimal;
};
using Literal = Address::Literal; using Literal = Address::Literal;
using ZeroPage = Address::ZeroPage; using ZeroPage = Address::ZeroPage;
@@ -101,16 +109,9 @@ void Processor<model, Traits>::run_for(const Cycles cycles) {
} }
// ADC and SBC decimal take an extra cycle on the 65c02. // ADC and SBC decimal take an extra cycle on the 65c02.
if constexpr (is_65c02(model)) { if(needs_65c02_extra_arithmetic_cycle()) {
if(
(
Storage::decoded_.operation == Operation::ADC ||
Storage::decoded_.operation == Operation::SBC
) && registers.flags.decimal
) {
goto access_zero_65c02_decimal; goto access_zero_65c02_decimal;
} }
}
// Read. // Read.
check_interrupt(); check_interrupt();
@@ -156,16 +157,9 @@ void Processor<model, Traits>::run_for(const Cycles cycles) {
} }
// ADC and SBC decimal take an extra cycle on the 65c02. // ADC and SBC decimal take an extra cycle on the 65c02.
if constexpr (is_65c02(model)) { if(needs_65c02_extra_arithmetic_cycle()) {
if(
(
Storage::decoded_.operation == Operation::ADC ||
Storage::decoded_.operation == Operation::SBC
) && registers.flags.decimal
) {
goto access_absolute_65c02_decimal; goto access_absolute_65c02_decimal;
} }
}
// Read. // Read.
check_interrupt(); check_interrupt();
@@ -235,6 +229,9 @@ void Processor<model, Traits>::run_for(const Cycles cycles) {
// MARK: - Immediate, Implied, Accumulator. // MARK: - Immediate, Implied, Accumulator.
case access_program(Immediate): case access_program(Immediate):
if(needs_65c02_extra_arithmetic_cycle()) {
goto immediate_65c02_decimal;
}
++registers.pc.full; ++registers.pc.full;
[[fallthrough]]; [[fallthrough]];
@@ -242,6 +239,14 @@ void Processor<model, Traits>::run_for(const Cycles cycles) {
perform_operation(); perform_operation();
goto fetch_decode; goto fetch_decode;
immediate_65c02_decimal:
check_interrupt();
access(BusOperation::Read, Literal(registers.pc.full), Storage::operand_);
++registers.pc.full;
perform_operation();
goto fetch_decode;
case access_program(Accumulator): case access_program(Accumulator):
CPU::MOS6502Mk2::perform<model>( CPU::MOS6502Mk2::perform<model>(
Storage::decoded_.operation, Storage::decoded_.operation,