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st2205u: DMA required by PR #7430 (#7444)

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David Haywood 2020-11-12 17:42:56 +00:00 committed by GitHub
parent 494b7ef63f
commit c13709f111
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1 changed files with 20 additions and 2 deletions
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22
src/devices/cpu/m6502/st2205u.cpp
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@ -926,8 +926,26 @@ u8 st2205u_base_device::dcnth_r()
void st2205u_base_device::dcnth_w(u8 data)
{
m_dcnt[m_dctr >> 1] = (m_dcnt[m_dctr >> 1] & 0x7f00) | data;
// TODO: start DMA here
m_dcnt[m_dctr >> 1] = (data & 0x7f) << 8 | (m_dcnt[m_dctr >> 1] & 0x00ff);
// start DMA
int source = m_dptr[(m_dctr & 2) + 0];
int dest = m_dptr[(m_dctr & 2) + 1];
int length = m_dcnt[m_dctr >> 1] << 1;
if ((m_dbkr[(m_dctr & 2) + 0] != 0x8000) || (m_dbkr[(m_dctr & 2) + 1] != 0x8000) || (m_dmod[m_dctr >> 1] != 0x30))
logerror("%s: unhandled DMA parameter %04x %04x %02x\n", machine().describe_context(), m_dbkr[(m_dctr & 2) + 0], m_dbkr[(m_dctr & 2) + 1], m_dmod[m_dctr >> 1]);
address_space& mem = this->space(AS_PROGRAM);
// FIXME: DMA should be performed in the execution loop and consume bus cycles, not happen instantly
for (int i = 0; i < length; i++)
{
uint8_t byte = mem.read_byte(source);
mem.write_byte(dest, byte);
source++;
dest++;
}
}
u8 st2205u_base_device::dctr_r()