Genesis-Plus-GX/source/memz80.c

247 lines
5.4 KiB
C
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2007-08-10 22:34:06 +02:00
/*
memz80.c --
Memory handlers for Z80 memory and port access, and the Z80 to
VDP interface.
*/
#define LOG_PORT 0 /* 1= Log Z80 I/O port accesses */
#include "shared.h"
unsigned int cpu_readmem16(unsigned int address)
{
switch((address >> 13) & 7)
{
case 0: /* Work RAM */
case 1:
return zram[address & 0x1FFF];
case 2: /* YM2612 */
return fm_read(address & 3);
case 3: /* VDP */
if ((address & 0xFF00) == 0x7F00) return z80_vdp_r (address);
return 0xFF;
default: /* V-bus bank */
return z80_read_banked_memory(zbank | (address & 0x7FFF));
}
return 0xFF;
}
void cpu_writemem16(unsigned int address, unsigned int data)
{
switch((address >> 13) & 7)
{
case 0: /* Work RAM */
case 1:
zram[address & 0x1FFF] = data;
return;
case 2: /* YM2612 */
fm_write(address & 3, data);
return;
case 3: /* Bank register and VDP */
switch(address & 0xFF00)
{
case 0x6000:
gen_bank_w(data & 1);
return;
case 0x7F00:
z80_vdp_w(address, data);
return;
default:
z80_unused_w(address, data);
return;
}
return;
default: /* V-bus bank */
z80_write_banked_memory(zbank | (address & 0x7FFF), data);
return;
}
}
int z80_vdp_r(int address)
{
switch(address & 0xFF)
{
case 0x00: /* VDP data port */
case 0x02:
return (vdp_data_r() >> 8) & 0xFF;
case 0x01: /* VDP data port */
case 0x03:
return (vdp_data_r() & 0xFF);
case 0x04: /* VDP control port */
case 0x06:
return (0xFF | ((vdp_ctrl_r() >> 8) & 3));
case 0x05: /* VDP control port */
case 0x07:
return (vdp_ctrl_r() & 0xFF);
case 0x08: /* HV counter */
case 0x0A:
case 0x0C:
case 0x0E:
return (vdp_hvc_r() >> 8) & 0xFF;
case 0x09: /* HV counter */
case 0x0B:
case 0x0D:
case 0x0F:
return (vdp_hvc_r() & 0xFF);
case 0x10: /* Unused (PSG) */
case 0x11:
case 0x12:
case 0x13:
case 0x14:
case 0x15:
case 0x16:
case 0x17:
return z80_lockup_r(address);
case 0x18: /* Unused */
case 0x19:
case 0x1A:
case 0x1B:
return z80_unused_r(address);
case 0x1C: /* Unused (test register) */
case 0x1D:
case 0x1E:
case 0x1F:
return z80_unused_r(address);
default: /* Invalid VDP addresses */
return z80_lockup_r(address);
}
return 0xFF;
}
void z80_vdp_w(int address, int data)
{
switch(address & 0xFF)
{
case 0x00: /* VDP data port */
case 0x01:
case 0x02:
case 0x03:
vdp_data_w(data << 8 | data);
return;
case 0x04: /* VDP control port */
case 0x05:
case 0x06:
case 0x07:
vdp_ctrl_w(data << 8 | data);
return;
case 0x08: /* Unused (HV counter) */
case 0x09:
case 0x0A:
case 0x0B:
case 0x0C:
case 0x0D:
case 0x0E:
case 0x0F:
z80_lockup_w(address, data);
return;
case 0x11: /* PSG */
case 0x13:
case 0x15:
case 0x17:
psg_write(data);
return;
case 0x10: /* Unused */
case 0x12:
case 0x14:
case 0x16:
case 0x18:
case 0x19:
case 0x1A:
case 0x1B:
z80_unused_w(address, data);
return;
case 0x1C: /* Test register */
case 0x1D:
case 0x1E:
case 0x1F:
vdp_test_w(data << 8 | data);
return;
default: /* Invalid VDP addresses */
z80_lockup_w(address, data);
return;
}
}
/*
Port handlers. Ports are unused when not in Mark III compatability mode.
Games that access ports anyway:
- Thunder Force IV reads port $BF in it's interrupt handler.
*/
unsigned int cpu_readport16(unsigned int port)
{
#if LOG_PORT
error("Z80 read port %04X (%04X)\n", port, z80_get_reg(Z80_PC));
#endif
return 0xFF;
}
void cpu_writeport16(unsigned int port, unsigned int data)
{
#if LOG_PORT
error("Z80 write %02X to port %04X (%04X)\n", data, port, z80_get_reg(Z80_PC));
#endif
}
/*
Handlers for access to unused addresses and those which make the
machine lock up.
*/
void z80_unused_w(int address, int data)
{
error("Z80 unused write %04X = %02X (%04X)\n", address, data, z80_get_reg(Z80_PC));
}
int z80_unused_r(int address)
{
error("Z80 unused read %04X (%04X)\n", address, z80_get_reg(Z80_PC));
return 0xFF;
}
void z80_lockup_w(int address, int data)
{
error("Z80 lockup write %04X = %02X (%04X)\n", address, data, z80_get_reg(Z80_PC));
gen_running = 0;
z80_end_timeslice();
}
int z80_lockup_r(int address)
{
error("Z80 lockup read %04X (%04X)\n", address, z80_get_reg(Z80_PC));
gen_running = 0;
z80_end_timeslice();
return 0xFF;
}