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add feature to the cia6526: in READ operation the value can be forced by a extern electric circuit; this feature is necessary to the mess side

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This commit is contained in:
Roberto Zandona 2008-05-07 07:01:48 +00:00
parent e85ce6581d
commit 4c138a09fc
2 changed files with 13 additions and 3 deletions
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15
src/emu/machine/6526cia.c
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@ -67,6 +67,7 @@ struct _cia_port
UINT8 out;
UINT8 (*read)(void);
void (*write)(UINT8);
UINT8 mask_value; /* in READ operation the value can be forced by a extern electric circuit */
};
struct _cia_state
@ -166,6 +167,7 @@ void cia_config(int which, const cia6526_interface *intf)
{
cia->port[p].read = intf->port[p].read;
cia->port[p].write = intf->port[p].write;
cia->port[p].mask_value = 0xff;
}
/* setup timers */
@ -190,10 +192,12 @@ void cia_config(int which, const cia6526_interface *intf)
state_save_register_item("6526cia", which, cia->port[0].latch);
state_save_register_item("6526cia", which, cia->port[0].in);
state_save_register_item("6526cia", which, cia->port[0].out);
state_save_register_item("6526cia", which, cia->port[0].mask_value);
state_save_register_item("6526cia", which, cia->port[1].ddr);
state_save_register_item("6526cia", which, cia->port[1].latch);
state_save_register_item("6526cia", which, cia->port[1].in);
state_save_register_item("6526cia", which, cia->port[1].out);
state_save_register_item("6526cia", which, cia->port[1].mask_value);
state_save_register_item("6526cia", which, cia->timer[0].latch);
state_save_register_item("6526cia", which, cia->timer[0].count);
state_save_register_item("6526cia", which, cia->timer[0].mode);
@ -218,7 +222,11 @@ void cia_config(int which, const cia6526_interface *intf)
state_save_register_item("6526cia", which, cia->serial);
}
void cia_set_port_mask_value(int which, int p, int data)
{
cia_state *cia = &cia_array[which];
cia->port[p].mask_value = data;
}
void cia_reset(void)
{
@ -235,9 +243,11 @@ void cia_reset(void)
cia->port[0].latch = 0x00;
cia->port[0].in = 0x00;
cia->port[0].out = 0x00;
cia->port[0].mask_value = 0xff;
cia->port[1].latch = 0x00;
cia->port[1].in = 0x00;
cia->port[1].out = 0x00;
cia->port[0].mask_value = 0xff;
cia->tod = 0;
cia->tod_latch = 0;
cia->alarm = 0;
@ -569,8 +579,7 @@ UINT8 cia_read(int which, offs_t offset)
case CIA_PRB:
port = &cia->port[offset & 1];
data = port->read ? (*port->read)() : 0;
//data = data & (port->latch | ~port->ddr);
data = (data & ~port->ddr) | (port->latch & port->ddr);
data = ((data & ~port->ddr) | (port->latch & port->ddr)) & port->mask_value;
port->in = data;
if (offset == CIA_PRB)

1
src/emu/machine/6526cia.h
View File

@ -34,6 +34,7 @@ struct _cia6526_interface
/* configuration and reset */
void cia_config(int which, const cia6526_interface *intf);
void cia_reset(void);
void cia_set_port_mask_value(int which, int p, int data);
/* reading and writing */
UINT8 cia_read(int which, offs_t offset);