6502/CLK
1
0
Fork 0
mirror of https://github.com/TomHarte/CLK.git synced 2025-01-11 08:30:55 +00:00
Code Issues Projects Releases Wiki Activity

Sketched an interface for signalling interrupts and pulled out some of the repetition in flag setting from ADD/ADC/SUB/SBC/CP.

Browse Source
This commit is contained in:
Thomas Harte 2017-05-31 22:51:32 -04:00
parent a5254989f8
commit c9dd267ec1
1 changed files with 58 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

95
Processors/Z80/Z80.hpp
View File

@ -779,97 +779,81 @@ template <class T> class Processor: public MicroOpScheduler<MicroOp> {
#pragma mark - 8-bit arithmetic
#define set_arithmetic_flags(sub, b53) \
sign_result_ = zero_result_ = (uint8_t)result; \
carry_result_ = result >> 8; \
half_carry_result_ = half_result; \
parity_overflow_result_ = overflow >> 5; \
subtract_flag_ = sub; \
bit53_result_ = (uint8_t)b53;
case MicroOp::CP8: {
uint8_t value = *(uint8_t *)operation->source;
int result = a_ - value;
int halfResult = (a_&0xf) - (value&0xf);
int half_result = (a_&0xf) - (value&0xf);
// overflow for a subtraction is when the signs were originally
// different and the result is different again
int overflow = (value^a_) & (result^a_);
sign_result_ = // set sign and zero
zero_result_ = (uint8_t)result;
bit53_result_ = value; // set the 5 and 3 flags, which come
// from the operand atypically
carry_result_ = result >> 8;
half_carry_result_ = halfResult;
parity_overflow_result_ = overflow >> 5;
subtract_flag_ = Flag::Subtract;
// the 5 and 3 flags come from the operand, atypically
set_arithmetic_flags(Flag::Subtract, value);
} break;
case MicroOp::SUB8: {
uint8_t value = *(uint8_t *)operation->source;
int result = a_ - value;
int halfResult = (a_&0xf) - (value&0xf);
int half_result = (a_&0xf) - (value&0xf);
// overflow for a subtraction is when the signs were originally
// different and the result is different again
int overflow = (value^a_) & (result^a_);
a_ = (uint8_t)result;
sign_result_ = zero_result_ = bit53_result_ = (uint8_t)result;
carry_result_ = result >> 8;
half_carry_result_ = halfResult;
parity_overflow_result_ = overflow >> 5;
subtract_flag_ = Flag::Subtract;
set_arithmetic_flags(Flag::Subtract, result);
} break;
case MicroOp::SBC8: {
uint8_t value = *(uint8_t *)operation->source;
int result = a_ - value - (carry_result_ & Flag::Carry);
int halfResult = (a_&0xf) - (value&0xf) - (carry_result_ & Flag::Carry);
int half_result = (a_&0xf) - (value&0xf) - (carry_result_ & Flag::Carry);
// overflow for a subtraction is when the signs were originally
// different and the result is different again
int overflow = (value^a_) & (result^a_);
a_ = (uint8_t)result;
sign_result_ = zero_result_ = bit53_result_ = (uint8_t)result;
carry_result_ = result >> 8;
half_carry_result_ = halfResult;
parity_overflow_result_ = overflow >> 5;
subtract_flag_ = Flag::Subtract;
set_arithmetic_flags(Flag::Subtract, result);
} break;
case MicroOp::ADD8: {
uint8_t value = *(uint8_t *)operation->source;
int result = a_ + value;
int halfResult = (a_&0xf) + (value&0xf);
int half_result = (a_&0xf) + (value&0xf);
// overflow for addition is when the signs were originally
// the same and the result is different
int overflow = ~(value^a_) & (result^a_);
a_ = (uint8_t)result;
sign_result_ = zero_result_ = bit53_result_ = (uint8_t)result;
carry_result_ = result >> 8;
half_carry_result_ = halfResult;
parity_overflow_result_ = overflow >> 5;
subtract_flag_ = 0;
set_arithmetic_flags(0, result);
} break;
case MicroOp::ADC8: {
uint8_t value = *(uint8_t *)operation->source;
int result = a_ + value + (carry_result_ & Flag::Carry);
int halfResult = (a_&0xf) + (value&0xf) + (carry_result_ & Flag::Carry);
int half_result = (a_&0xf) + (value&0xf) + (carry_result_ & Flag::Carry);
// overflow for addition is when the signs were originally
// the same and the result is different
int overflow = ~(value^a_) & (result^a_);
a_ = (uint8_t)result;
sign_result_ = zero_result_ = bit53_result_ = (uint8_t)result;
carry_result_ = result >> 8;
half_carry_result_ = halfResult;
parity_overflow_result_ = overflow >> 5;
subtract_flag_ = 0;
set_arithmetic_flags(0, result);
} break;
#undef set_arithmetic_flags
case MicroOp::NEG: {
int overflow = (a_ == 0x80);
int result = -a_;
@ -1582,6 +1566,43 @@ template <class T> class Processor: public MicroOpScheduler<MicroOp> {
bool get_halt_line() {
return halt_mask_ == 0x00;
}
/*!
Sets the logical value of the interrupt line at @c time_offset cycles from now.
*/
void set_interrupt_line(bool value, int time_offset) {
}
/*!
Sets the logical value of the non-maskable interrupt line at @c time_offset cycles from now.
*/
void set_non_maskable_interrupt_line(bool value, int time_offset) {
}
/*!
Sets the logical value of the bus request line at @c time_offset cycles from now.
*/
void set_bus_request_line(bool value, int time_offset) {
}
/*!
For receivers of perform_machine_cycle only. Temporarily rejects the current machine
cycle, causing time to be rewinded to its beginning.
Behaviour will be to cause the Z80 to repeat this machine cycle, having adjusted total
running time appropriately. This method is intended for use if a subclass receives
perform_machine_cycle, indicating that the cycle should be completed, and discovers
that it should have signalled IRQ, NMI or BUSREQ during the cycle. In that case it
can rewind time and post the signal with a proper time offset.
*/
void reject_machine_cycle() {
}
/*!
Returns the bus cycle that the Z80 is currently in the process of performing.
*/
const MachineCycle &get_current_bus_cycle(int &cycles_since_start) {
}
};
}