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(MESS) Apple II: enforce read twice requirement for language card. [R. Belmont]

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This commit is contained in:
R. Belmont 2014-05-04 18:40:39 +00:00
parent 4177846c42
commit 3bd7b0175a
2 changed files with 21 additions and 0 deletions
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19
src/emu/bus/a2bus/a2lang.c
View File

@ -36,12 +36,14 @@ a2bus_lang_device::a2bus_lang_device(const machine_config &mconfig, const char *
device_t(mconfig, A2BUS_LANG, "Apple II Language Card", tag, owner, clock, "a2lang", __FILE__),
device_a2bus_card_interface(mconfig, *this)
{
last_offset = -1;
}
a2bus_lang_device::a2bus_lang_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock, const char *shortname, const char *source) :
device_t(mconfig, type, name, tag, owner, clock, shortname, source),
device_a2bus_card_interface(mconfig, *this)
{
last_offset = -1;
}
//-------------------------------------------------
@ -52,6 +54,8 @@ void a2bus_lang_device::device_start()
{
// set_a2bus_device makes m_slot valid
set_a2bus_device();
save_item(NAME(last_offset));
}
void a2bus_lang_device::device_reset()
@ -100,7 +104,21 @@ void a2bus_lang_device::langcard_touch(offs_t offset)
UINT8 a2bus_lang_device::read_c0nx(address_space &space, UINT8 offset)
{
// enforce "read twice" for c081/3/9/B
switch(offset & 0x03)
{
case 1:
case 3:
if (offset != last_offset)
{
last_offset = offset;
return 0;
}
break;
}
langcard_touch(offset);
last_offset = offset;
return 0;
}
@ -113,4 +131,5 @@ UINT8 a2bus_lang_device::read_c0nx(address_space &space, UINT8 offset)
void a2bus_lang_device::write_c0nx(address_space &space, UINT8 offset, UINT8 data)
{
langcard_touch(offset);
last_offset = -1;
}

2
src/emu/bus/a2bus/a2lang.h
View File

@ -34,6 +34,8 @@ protected:
private:
void langcard_touch(offs_t offset);
int last_offset;
};
// device type definition