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Added a direct-to-two-cycles emulation path for 6522 owners.

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This commit is contained in:
Thomas Harte 2016-10-27 21:13:25 -04:00
parent 2eda0b3c86
commit 4fab794747
4 changed files with 40 additions and 19 deletions
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45
Components/6522/6522.hpp
View File

@ -230,18 +230,6 @@ template <class T> class MOS6522 {
}
}
/*!
Runs for a specified number of half cycles.
Although the original chip accepts only a phase-2 input, timer reloads are specified as occuring
1.5 cycles after the timer hits zero. It is therefore necessary to emulate at half-cycle precision.
The first emulated half-cycle will be the period between the trailing edge of a phase-2 input and the
next rising edge. So it should align with a full system's phase-1. The next emulated half-cycle will be
that which occurs during phase-2.
*/
inline void run_for_half_cycles(unsigned int number_of_cycles)
{
#define phase2() \
_registers.last_timer[0] = _registers.timer[0];\
_registers.last_timer[1] = _registers.timer[1];\
@ -276,6 +264,21 @@ template <class T> class MOS6522 {
_timer_is_running[0] = false;\
}
/*!
Runs for a specified number of half cycles.
Although the original chip accepts only a phase-2 input, timer reloads are specified as occuring
1.5 cycles after the timer hits zero. It therefore may be necessary to emulate at half-cycle precision.
The first emulated half-cycle will be the period between the trailing edge of a phase-2 input and the
next rising edge. So it should align with a full system's phase-1. The next emulated half-cycle will be
that which occurs during phase-2.
Callers should decide whether they are going to use @c run_for_half_cycles or @c run_for_cycles, and not
intermingle usage.
*/
inline void run_for_half_cycles(unsigned int number_of_cycles)
{
if(_is_phase2)
{
phase2();
@ -300,6 +303,24 @@ template <class T> class MOS6522 {
}
}
/*!
Runs for a specified number of cycles.
Callers should decide whether they are going to use @c run_for_half_cycles or @c run_for_cycles, and not
intermingle usage.
*/
inline void run_for_cycles(unsigned int number_of_cycles)
{
while(number_of_cycles--)
{
phase1();
phase2();
}
}
#undef phase1
#undef phase2
/*! @returns @c true if the IRQ line is currently active; @c false otherwise. */
inline bool get_interrupt_line()
{

4
Machines/Commodore/1540/C1540.cpp
View File

@ -91,8 +91,8 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
_driveVIA.set_register(address, *value);
}
_serialPortVIA->run_for_half_cycles(2);
_driveVIA.run_for_half_cycles(2);
_serialPortVIA->run_for_cycles(1);
_driveVIA.run_for_cycles(1);
return 1;
}

8
Machines/Commodore/Vic-20/Vic20.cpp
View File

@ -139,8 +139,8 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
{
while(!_userPortVIA->get_interrupt_line() && !_keyboardVIA->get_interrupt_line() && !_tape.get_tape()->is_at_end())
{
_userPortVIA->run_for_half_cycles(2);
_keyboardVIA->run_for_half_cycles(2);
_userPortVIA->run_for_cycles(1);
_keyboardVIA->run_for_cycles(1);
_tape.run_for_cycles(1);
}
}
@ -157,8 +157,8 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
}
}
_userPortVIA->run_for_half_cycles(2);
_keyboardVIA->run_for_half_cycles(2);
_userPortVIA->run_for_cycles(1);
_keyboardVIA->run_for_cycles(1);
if(_typer && operation == CPU6502::BusOperation::ReadOpcode && address == 0xEB1E)
{
if(!_typer->type_next_character())

2
Machines/Oric/Oric.cpp
View File

@ -61,7 +61,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
}
}
_via.run_for_half_cycles(2);
_via.run_for_cycles(1);
_via.tape->run_for_cycles(1);
_cycles_since_video_update++;
return 1;