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frodo-wii/Src/CPUC64.cpp
simon.kagstrom 2a6bece89d Imported orig code
2008-12-31 16:16:24 +00:00

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/*
* CPUC64.cpp - 6510 (C64) emulation (line based)
*
* Frodo (C) 1994-1997,2002 Christian Bauer
*
*
* Notes:
* ------
*
* - The EmulateLine() function is called for every emulated
* raster line. It has a cycle counter that is decremented
* by every executed opcode and if the counter goes below
* zero, the function returns.
* - Memory configurations:
* $01 $a000-$bfff $d000-$dfff $e000-$ffff
* -----------------------------------------------
* 0 RAM RAM RAM
* 1 RAM Char ROM RAM
* 2 RAM Char ROM Kernal ROM
* 3 Basic ROM Char ROM Kernal ROM
* 4 RAM RAM RAM
* 5 RAM I/O RAM
* 6 RAM I/O Kernal ROM
* 7 Basic ROM I/O Kernal ROM
* - All memory accesses are done with the read_byte() and
* write_byte() functions which also do the memory address
* decoding. The read_zp() and write_zp() functions allow
* faster access to the zero page, the pop_byte() and
* push_byte() macros for the stack.
* - If a write occurs to addresses 0 or 1, new_config is
* called to check whether the memory configuration has
* changed
* - The PC is either emulated with a 16 bit address or a
* direct memory pointer (for faster access), depending on
* the PC_IS_POINTER #define. In the latter case, a second
* pointer, pc_base, is kept to allow recalculating the
* 16 bit 6510 PC if it has to be pushed on the stack.
* - The possible interrupt sources are:
* INT_VICIRQ: I flag is checked, jump to ($fffe)
* INT_CIAIRQ: I flag is checked, jump to ($fffe)
* INT_NMI: Jump to ($fffa)
* INT_RESET: Jump to ($fffc)
* - Interrupts are not checked before every opcode but only
* at certain times:
* On entering EmulateLine()
* On CLI
* On PLP if the I flag was cleared
* On RTI if the I flag was cleared
* - The z_flag variable has the inverse meaning of the
* 6510 Z flag
* - Only the highest bit of the n_flag variable is used
* - The $f2 opcode that would normally crash the 6510 is
* used to implement emulator-specific functions, mainly
* those for the IEC routines
*
* Incompatibilities:
* ------------------
*
* - If PC_IS_POINTER is set, neither branches accross memory
* areas nor jumps to I/O space are possible
* - Extra cycles for crossing page boundaries are not
* accounted for
* - The cassette sense line is always closed
*/
#include "sysdeps.h"
#include "CPUC64.h"
#include "C64.h"
#include "VIC.h"
#include "SID.h"
#include "CIA.h"
#include "REU.h"
#include "IEC.h"
#include "Display.h"
#include "Version.h"
enum {
INT_RESET = 3
};
/*
* 6510 constructor: Initialize registers
*/
MOS6510::MOS6510(C64 *c64, uint8 *Ram, uint8 *Basic, uint8 *Kernal, uint8 *Char, uint8 *Color)
: the_c64(c64), ram(Ram), basic_rom(Basic), kernal_rom(Kernal), char_rom(Char), color_ram(Color)
{
a = x = y = 0;
sp = 0xff;
n_flag = z_flag = 0;
v_flag = d_flag = c_flag = false;
i_flag = true;
dfff_byte = 0x55;
borrowed_cycles = 0;
}
/*
* Reset CPU asynchronously
*/
void MOS6510::AsyncReset(void)
{
interrupt.intr[INT_RESET] = true;
}
/*
* Raise NMI asynchronously (Restore key)
*/
void MOS6510::AsyncNMI(void)
{
if (!nmi_state)
interrupt.intr[INT_NMI] = true;
}
/*
* Memory configuration has probably changed
*/
void MOS6510::new_config(void)
{
uint8 port = ~ram[0] | ram[1];
basic_in = (port & 3) == 3;
kernal_in = port & 2;
char_in = (port & 3) && !(port & 4);
io_in = (port & 3) && (port & 4);
}
/*
* Read a byte from I/O / ROM space
*/
inline uint8 MOS6510::read_byte_io(uint16 adr)
{
switch (adr >> 12) {
case 0xa:
case 0xb:
if (basic_in)
return basic_rom[adr & 0x1fff];
else
return ram[adr];
case 0xc:
return ram[adr];
case 0xd:
if (io_in)
switch ((adr >> 8) & 0x0f) {
case 0x0: // VIC
case 0x1:
case 0x2:
case 0x3:
return TheVIC->ReadRegister(adr & 0x3f);
case 0x4: // SID
case 0x5:
case 0x6:
case 0x7:
return TheSID->ReadRegister(adr & 0x1f);
case 0x8: // Color RAM
case 0x9:
case 0xa:
case 0xb:
return color_ram[adr & 0x03ff] | rand() & 0xf0;
case 0xc: // CIA 1
return TheCIA1->ReadRegister(adr & 0x0f);
case 0xd: // CIA 2
return TheCIA2->ReadRegister(adr & 0x0f);
case 0xe: // REU/Open I/O
case 0xf:
if ((adr & 0xfff0) == 0xdf00)
return TheREU->ReadRegister(adr & 0x0f);
else if (adr < 0xdfa0)
return rand();
else
return read_emulator_id(adr & 0x7f);
}
else if (char_in)
return char_rom[adr & 0x0fff];
else
return ram[adr];
case 0xe:
case 0xf:
if (kernal_in)
return kernal_rom[adr & 0x1fff];
else
return ram[adr];
default: // Can't happen
return 0;
}
}
/*
* Read a byte from the CPU's address space
*/
uint8 MOS6510::read_byte(uint16 adr)
{
if (adr < 0xa000)
return ram[adr];
else
return read_byte_io(adr);
}
/*
* $dfa0-$dfff: Emulator identification
*/
const char frodo_id[0x5c] = "FRODO\r(C) 1994-1997 CHRISTIAN BAUER";
uint8 MOS6510::read_emulator_id(uint16 adr)
{
switch (adr) {
case 0x7c: // $dffc: revision
return FRODO_REVISION << 4;
case 0x7d: // $dffd: version
return FRODO_VERSION;
case 0x7e: // $dffe returns 'F' (Frodo ID)
return 'F';
case 0x7f: // $dfff alternates between $55 and $aa
dfff_byte = ~dfff_byte;
return dfff_byte;
default:
return frodo_id[adr - 0x20];
}
}
/*
* Read a word (little-endian) from the CPU's address space
*/
#if LITTLE_ENDIAN_UNALIGNED
inline uint16 MOS6510::read_word(uint16 adr)
{
switch (adr >> 12) {
case 0x0:
case 0x1:
case 0x2:
case 0x3:
case 0x4:
case 0x5:
case 0x6:
case 0x7:
case 0x8:
case 0x9:
return *(uint16*)&ram[adr];
break;
case 0xa:
case 0xb:
if (basic_in)
return *(uint16*)&basic_rom[adr & 0x1fff];
else
return *(uint16*)&ram[adr];
case 0xc:
return *(uint16*)&ram[adr];
case 0xd:
if (io_in)
return read_byte(adr) | (read_byte(adr+1) << 8);
else if (char_in)
return *(uint16*)&char_rom[adr & 0x0fff];
else
return *(uint16*)&ram[adr];
case 0xe:
case 0xf:
if (kernal_in)
return *(uint16*)&kernal_rom[adr & 0x1fff];
else
return *(uint16*)&ram[adr];
default: // Can't happen
return 0;
}
}
#else
inline uint16 MOS6510::read_word(uint16 adr)
{
return read_byte(adr) | (read_byte(adr+1) << 8);
}
#endif
/*
* Write byte to I/O space
*/
void MOS6510::write_byte_io(uint16 adr, uint8 byte)
{
if (adr >= 0xe000) {
ram[adr] = byte;
if (adr == 0xff00)
TheREU->FF00Trigger();
} else if (io_in)
switch ((adr >> 8) & 0x0f) {
case 0x0: // VIC
case 0x1:
case 0x2:
case 0x3:
TheVIC->WriteRegister(adr & 0x3f, byte);
return;
case 0x4: // SID
case 0x5:
case 0x6:
case 0x7:
TheSID->WriteRegister(adr & 0x1f, byte);
return;
case 0x8: // Color RAM
case 0x9:
case 0xa:
case 0xb:
color_ram[adr & 0x03ff] = byte & 0x0f;
return;
case 0xc: // CIA 1
TheCIA1->WriteRegister(adr & 0x0f, byte);
return;
case 0xd: // CIA 2
TheCIA2->WriteRegister(adr & 0x0f, byte);
return;
case 0xe: // REU/Open I/O
case 0xf:
if ((adr & 0xfff0) == 0xdf00)
TheREU->WriteRegister(adr & 0x0f, byte);
return;
}
else
ram[adr] = byte;
}
/*
* Write a byte to the CPU's address space
*/
inline void MOS6510::write_byte(uint16 adr, uint8 byte)
{
if (adr < 0xd000) {
ram[adr] = byte;
if (adr < 2)
new_config();
} else
write_byte_io(adr, byte);
}
/*
* Read a byte from the zeropage
*/
inline uint8 MOS6510::read_zp(uint16 adr)
{
return ram[adr];
}
/*
* Read a word (little-endian) from the zeropage
*/
inline uint16 MOS6510::read_zp_word(uint16 adr)
{
// !! zeropage word addressing wraps around !!
#if LITTLE_ENDIAN_UNALIGNED
return *(uint16 *)&ram[adr & 0xff];
#else
return ram[adr & 0xff] | (ram[(adr+1) & 0xff] << 8);
#endif
}
/*
* Write a byte to the zeropage
*/
inline void MOS6510::write_zp(uint16 adr, uint8 byte)
{
ram[adr] = byte;
// Check if memory configuration may have changed.
if (adr < 2)
new_config();
}
/*
* Read byte from 6510 address space with special memory config (used by SAM)
*/
uint8 MOS6510::ExtReadByte(uint16 adr)
{
// Save old memory configuration
bool bi = basic_in, ki = kernal_in, ci = char_in, ii = io_in;
// Set new configuration
basic_in = (ExtConfig & 3) == 3;
kernal_in = ExtConfig & 2;
char_in = (ExtConfig & 3) && ~(ExtConfig & 4);
io_in = (ExtConfig & 3) && (ExtConfig & 4);
// Read byte
uint8 byte = read_byte(adr);
// Restore old configuration
basic_in = bi; kernal_in = ki; char_in = ci; io_in = ii;
return byte;
}
/*
* Write byte to 6510 address space with special memory config (used by SAM)
*/
void MOS6510::ExtWriteByte(uint16 adr, uint8 byte)
{
// Save old memory configuration
bool bi = basic_in, ki = kernal_in, ci = char_in, ii = io_in;
// Set new configuration
basic_in = (ExtConfig & 3) == 3;
kernal_in = ExtConfig & 2;
char_in = (ExtConfig & 3) && ~(ExtConfig & 4);
io_in = (ExtConfig & 3) && (ExtConfig & 4);
// Write byte
write_byte(adr, byte);
// Restore old configuration
basic_in = bi; kernal_in = ki; char_in = ci; io_in = ii;
}
/*
* Read byte from 6510 address space with current memory config (used by REU)
*/
uint8 MOS6510::REUReadByte(uint16 adr)
{
return read_byte(adr);
}
/*
* Write byte to 6510 address space with current memory config (used by REU)
*/
void MOS6510::REUWriteByte(uint16 adr, uint8 byte)
{
write_byte(adr, byte);
}
/*
* Jump to address
*/
#if PC_IS_POINTER
void MOS6510::jump(uint16 adr)
{
if (adr < 0xa000) {
pc = ram + adr;
pc_base = ram;
} else
switch (adr >> 12) {
case 0xa:
case 0xb:
if (basic_in) {
pc = basic_rom + (adr & 0x1fff);
pc_base = basic_rom - 0xa000;
} else {
pc = ram + adr;
pc_base = ram;
}
break;
case 0xc:
pc = ram + adr;
pc_base = ram;
break;
case 0xd:
if (io_in)
illegal_jump(pc-pc_base, adr);
else if (char_in) {
pc = char_rom + (adr & 0x0fff);
pc_base = char_rom - 0xd000;
} else {
pc = ram + adr;
pc_base = ram;
}
break;
case 0xe:
case 0xf:
if (kernal_in) {
pc = kernal_rom + (adr & 0x1fff);
pc_base = kernal_rom - 0xe000;
} else {
pc = ram + adr;
pc_base = ram;
}
break;
}
}
#else
inline void MOS6510::jump(uint16 adr)
{
pc = adr;
}
#endif
/*
* Adc instruction
*/
void MOS6510::do_adc(uint8 byte)
{
if (!d_flag) {
uint16 tmp;
// Binary mode
tmp = a + byte + (c_flag ? 1 : 0);
c_flag = tmp > 0xff;
v_flag = !((a ^ byte) & 0x80) && ((a ^ tmp) & 0x80);
z_flag = n_flag = a = tmp;
} else {
uint16 al, ah;
// Decimal mode
al = (a & 0x0f) + (byte & 0x0f) + (c_flag ? 1 : 0); // Calculate lower nybble
if (al > 9) al += 6; // BCD fixup for lower nybble
ah = (a >> 4) + (byte >> 4); // Calculate upper nybble
if (al > 0x0f) ah++;
z_flag = a + byte + (c_flag ? 1 : 0); // Set flags
n_flag = ah << 4; // Only highest bit used
v_flag = (((ah << 4) ^ a) & 0x80) && !((a ^ byte) & 0x80);
if (ah > 9) ah += 6; // BCD fixup for upper nybble
c_flag = ah > 0x0f; // Set carry flag
a = (ah << 4) | (al & 0x0f); // Compose result
}
}
/*
* Sbc instruction
*/
void MOS6510::do_sbc(uint8 byte)
{
uint16 tmp = a - byte - (c_flag ? 0 : 1);
if (!d_flag) {
// Binary mode
c_flag = tmp < 0x100;
v_flag = ((a ^ tmp) & 0x80) && ((a ^ byte) & 0x80);
z_flag = n_flag = a = tmp;
} else {
uint16 al, ah;
// Decimal mode
al = (a & 0x0f) - (byte & 0x0f) - (c_flag ? 0 : 1); // Calculate lower nybble
ah = (a >> 4) - (byte >> 4); // Calculate upper nybble
if (al & 0x10) {
al -= 6; // BCD fixup for lower nybble
ah--;
}
if (ah & 0x10) ah -= 6; // BCD fixup for upper nybble
c_flag = tmp < 0x100; // Set flags
v_flag = ((a ^ tmp) & 0x80) && ((a ^ byte) & 0x80);
z_flag = n_flag = tmp;
a = (ah << 4) | (al & 0x0f); // Compose result
}
}
/*
* Get 6510 register state
*/
void MOS6510::GetState(MOS6510State *s)
{
s->a = a;
s->x = x;
s->y = y;
s->p = 0x20 | (n_flag & 0x80);
if (v_flag) s->p |= 0x40;
if (d_flag) s->p |= 0x08;
if (i_flag) s->p |= 0x04;
if (!z_flag) s->p |= 0x02;
if (c_flag) s->p |= 0x01;
s->ddr = ram[0];
s->pr = ram[1] & 0x3f;
#if PC_IS_POINTER
s->pc = pc - pc_base;
#else
s->pc = pc;
#endif
s->sp = sp | 0x0100;
s->intr[INT_VICIRQ] = interrupt.intr[INT_VICIRQ];
s->intr[INT_CIAIRQ] = interrupt.intr[INT_CIAIRQ];
s->intr[INT_NMI] = interrupt.intr[INT_NMI];
s->intr[INT_RESET] = interrupt.intr[INT_RESET];
s->nmi_state = nmi_state;
s->dfff_byte = dfff_byte;
s->instruction_complete = true;
}
/*
* Restore 6510 state
*/
void MOS6510::SetState(MOS6510State *s)
{
a = s->a;
x = s->x;
y = s->y;
n_flag = s->p;
v_flag = s->p & 0x40;
d_flag = s->p & 0x08;
i_flag = s->p & 0x04;
z_flag = !(s->p & 0x02);
c_flag = s->p & 0x01;
ram[0] = s->ddr;
ram[1] = s->pr;
new_config();
jump(s->pc);
sp = s->sp & 0xff;
interrupt.intr[INT_VICIRQ] = s->intr[INT_VICIRQ];
interrupt.intr[INT_CIAIRQ] = s->intr[INT_CIAIRQ];
interrupt.intr[INT_NMI] = s->intr[INT_NMI];
interrupt.intr[INT_RESET] = s->intr[INT_RESET];
nmi_state = s->nmi_state;
dfff_byte = s->dfff_byte;
}
/*
* Reset CPU
*/
void MOS6510::Reset(void)
{
// Delete 'CBM80' if present
if (ram[0x8004] == 0xc3 && ram[0x8005] == 0xc2 && ram[0x8006] == 0xcd
&& ram[0x8007] == 0x38 && ram[0x8008] == 0x30)
ram[0x8004] = 0;
// Initialize extra 6510 registers and memory configuration
ram[0] = ram[1] = 0;
new_config();
// Clear all interrupt lines
interrupt.intr_any = 0;
nmi_state = false;
// Read reset vector
jump(read_word(0xfffc));
}
/*
* Illegal opcode encountered
*/
void MOS6510::illegal_op(uint8 op, uint16 at)
{
char illop_msg[80];
sprintf(illop_msg, "Illegal opcode %02x at %04x.", op, at);
ShowRequester(illop_msg, "Reset");
the_c64->Reset();
Reset();
}
/*
* Jump to illegal address space (PC_IS_POINTER only)
*/
void MOS6510::illegal_jump(uint16 at, uint16 to)
{
char illop_msg[80];
sprintf(illop_msg, "Jump to I/O space at %04x to %04x.", at, to);
ShowRequester(illop_msg, "Reset");
the_c64->Reset();
Reset();
}
/*
* Stack macros
*/
// Pop a byte from the stack
#define pop_byte() ram[(++sp) | 0x0100]
// Push a byte onto the stack
#define push_byte(byte) (ram[(sp--) & 0xff | 0x0100] = (byte))
// Pop processor flags from the stack
#define pop_flags() \
n_flag = tmp = pop_byte(); \
v_flag = tmp & 0x40; \
d_flag = tmp & 0x08; \
i_flag = tmp & 0x04; \
z_flag = !(tmp & 0x02); \
c_flag = tmp & 0x01;
// Push processor flags onto the stack
#define push_flags(b_flag) \
tmp = 0x20 | (n_flag & 0x80); \
if (v_flag) tmp |= 0x40; \
if (b_flag) tmp |= 0x10; \
if (d_flag) tmp |= 0x08; \
if (i_flag) tmp |= 0x04; \
if (!z_flag) tmp |= 0x02; \
if (c_flag) tmp |= 0x01; \
push_byte(tmp);
/*
* Emulate cycles_left worth of 6510 instructions
* Returns number of cycles of last instruction
*/
int MOS6510::EmulateLine(int cycles_left)
{
uint8 tmp, tmp2;
uint16 adr; // Used by read_adr_abs()!
int last_cycles = 0;
// Any pending interrupts?
if (interrupt.intr_any) {
handle_int:
if (interrupt.intr[INT_RESET])
Reset();
else if (interrupt.intr[INT_NMI]) {
interrupt.intr[INT_NMI] = false; // Simulate an edge-triggered input
#if PC_IS_POINTER
push_byte((pc-pc_base) >> 8); push_byte(pc-pc_base);
#else
push_byte(pc >> 8); push_byte(pc);
#endif
push_flags(false);
i_flag = true;
jump(read_word(0xfffa));
last_cycles = 7;
} else if ((interrupt.intr[INT_VICIRQ] || interrupt.intr[INT_CIAIRQ]) && !i_flag) {
#if PC_IS_POINTER
push_byte((pc-pc_base) >> 8); push_byte(pc-pc_base);
#else
push_byte(pc >> 8); push_byte(pc);
#endif
push_flags(false);
i_flag = true;
jump(read_word(0xfffe));
last_cycles = 7;
}
}
#include "CPU_emulline.i"
// Extension opcode
case 0xf2:
#if PC_IS_POINTER
if ((pc-pc_base) < 0xe000) {
illegal_op(0xf2, pc-pc_base-1);
#else
if (pc < 0xe000) {
illegal_op(0xf2, pc-1);
#endif
break;
}
switch (read_byte_imm()) {
case 0x00:
ram[0x90] |= TheIEC->Out(ram[0x95], ram[0xa3] & 0x80);
c_flag = false;
jump(0xedac);
break;
case 0x01:
ram[0x90] |= TheIEC->OutATN(ram[0x95]);
c_flag = false;
jump(0xedac);
break;
case 0x02:
ram[0x90] |= TheIEC->OutSec(ram[0x95]);
c_flag = false;
jump(0xedac);
break;
case 0x03:
ram[0x90] |= TheIEC->In(&a);
set_nz(a);
c_flag = false;
jump(0xedac);
break;
case 0x04:
TheIEC->SetATN();
jump(0xedfb);
break;
case 0x05:
TheIEC->RelATN();
jump(0xedac);
break;
case 0x06:
TheIEC->Turnaround();
jump(0xedac);
break;
case 0x07:
TheIEC->Release();
jump(0xedac);
break;
default:
#if PC_IS_POINTER
illegal_op(0xf2, pc-pc_base-1);
#else
illegal_op(0xf2, pc-1);
#endif
break;
}
break;
}
}
return last_cycles;
}
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