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i8244: fix recent regression

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This commit is contained in:
hap 2021-01-22 21:23:53 +01:00
parent 1eb22dd22c
commit d40990b628
1 changed files with 6 additions and 5 deletions
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11
src/devices/video/i8244.cpp
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@ -286,12 +286,12 @@ u8 i8244_device::read(offs_t offset)
default: default:
data = m_vdc.reg[offset]; data = m_vdc.reg[offset];
// object x/y/attr registers are not readable when display is enabled // object x/y/attr registers are not accessible when display is enabled
// (sprite shape registers still are) // (sprite shape registers still are)
if (offset < 0x80 && m_vdc.s.control & 0x20) if (offset < 0x80 && m_vdc.s.control & 0x20)
data = 0; data = 0;
// grid registers are not readable when grid is enabled // grid registers are not accessible when grid is enabled
else if (offset >= 0xc0 && m_vdc.s.control & 0x08) else if (offset >= 0xc0 && m_vdc.s.control & 0x08)
data = 0; data = 0;
@ -306,8 +306,9 @@ void i8244_device::write(offs_t offset, u8 data)
{ {
offset = fix_register_mirrors(offset); offset = fix_register_mirrors(offset);
// object registers are not accessible when display is enabled // object x/y/attr registers are not accessible when display is enabled
if (offset < 0xa0 && m_vdc.s.control & 0x20) // (sprite shape registers still are)
if (offset < 0x80 && m_vdc.s.control & 0x20)
return; return;
// grid registers are not accessible when grid is enabled // grid registers are not accessible when grid is enabled
@ -316,7 +317,7 @@ void i8244_device::write(offs_t offset, u8 data)
return; return;
// update screen before accessing video registers // update screen before accessing video registers
if ((offset == 0xa0 || offset == 0xa2 || offset == 0xa3) && data != m_vdc.reg[offset]) if ((offset <= 0xa0 || offset == 0xa2 || offset == 0xa3) && data != m_vdc.reg[offset])
screen().update_now(); screen().update_now();
// color registers d4-d7 are not connected // color registers d4-d7 are not connected