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ti99: Changed behaviour of memory cells (invert even addresses), may

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help with some programs that assume power-on default values. (nw)
This commit is contained in:
Michael Zapf 2013-06-08 12:32:49 +00:00
parent fe024709e1
commit e8ce03e326
1 changed files with 18 additions and 8 deletions
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26
src/mess/machine/ti99/ti32kmem.c
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@ -36,40 +36,50 @@ ti_32k_expcard_device::ti_32k_expcard_device(const machine_config &mconfig, cons
READ8Z_MEMBER(ti_32k_expcard_device::readz)
{
UINT8 val = 0;
bool access = true;
switch((offset & 0xe000)>>13)
{
case 1:
*value = m_ram_ptr[offset & 0x1fff];
val = m_ram_ptr[offset & 0x1fff];
break;
case 5:
*value = m_ram_ptr[(offset & 0x1fff) | 0x2000];
val = m_ram_ptr[(offset & 0x1fff) | 0x2000];
break;
case 6:
*value = m_ram_ptr[(offset & 0x1fff) | 0x4000];
val = m_ram_ptr[(offset & 0x1fff) | 0x4000];
break;
case 7:
*value = m_ram_ptr[(offset & 0x1fff) | 0x6000];
val = m_ram_ptr[(offset & 0x1fff) | 0x6000];
break;
default:
access = false;
break;
}
if (access)
{
if ((offset&1)!=1) *value = ~val;
else *value = val;
}
}
WRITE8_MEMBER(ti_32k_expcard_device::write)
{
UINT8 data1 = data;
if ((offset&1)!=1) data1 = ~data;
switch((offset & 0xe000)>>13)
{
case 1:
m_ram_ptr[offset & 0x1fff] = data;
m_ram_ptr[offset & 0x1fff] = data1;
break;
case 5:
m_ram_ptr[(offset & 0x1fff) | 0x2000] = data;
m_ram_ptr[(offset & 0x1fff) | 0x2000] = data1;
break;
case 6:
m_ram_ptr[(offset & 0x1fff) | 0x4000] = data;
m_ram_ptr[(offset & 0x1fff) | 0x4000] = data1;
break;
case 7:
m_ram_ptr[(offset & 0x1fff) | 0x6000] = data;
m_ram_ptr[(offset & 0x1fff) | 0x6000] = data1;
break;
default:
break;