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(MESS) apple2: IIe and later don't require double-reads on the language card. [R. Belmont, Peter Ferrie]

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This commit is contained in:
R. Belmont 2014-10-05 17:07:01 +00:00
parent 942be9e4f9
commit d99fd52d67
1 changed files with 17 additions and 9 deletions
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26
src/emu/bus/a2bus/a2lang.c
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@ -104,17 +104,25 @@ void a2bus_lang_device::langcard_touch(offs_t offset)
UINT8 a2bus_lang_device::read_c0nx(address_space &space, UINT8 offset)
{
apple2_state *state = machine().driver_data<apple2_state>();
// enforce "read twice" for c081/3/9/B
switch(offset & 0x03)
// but only on the II/II+ with a discrete language card.
// later machines' ASICs dropped the double-read requirement,
// likely to be interrupt-safe.
if (state->m_machinetype == APPLE_II)
{
case 1:
case 3:
if (offset != last_offset)
{
last_offset = offset;
return 0;
}
break;
switch (offset & 0x03)
{
case 1:
case 3:
if (offset != last_offset)
{
last_offset = offset;
return 0;
}
break;
}
}
langcard_touch(offset);