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z180asci: Fix calculation of framing and parity errors

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This commit is contained in:
AJR 2024-10-21 17:07:02 -04:00
parent 575f1bb883
commit 759ea6d42c
1 changed files with 6 additions and 6 deletions
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12
src/devices/cpu/z180/z180asci.cpp
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@ -463,31 +463,31 @@ void z180asci_channel_base::transmit_edge()
void z180asci_channel_base::update_received()
{
uint8_t rx_error = 0;
int stop_bits = (m_asci_cntla & Z180_CNTLA_MODE_STOPB) ? 2 : 1;
int data_bits = (m_asci_cntla & Z180_CNTLA_MODE_DATA) ? 8 : 7;
if (m_rsr == 0) // Break detect
{
m_asci_ext |= Z180_ASEXT_BRK_DET;
}
uint8_t stop_val = (m_asci_cntla & Z180_CNTLA_MODE_STOPB) ? 3: 1;
if ((m_rsr & stop_val) != stop_val)
if (m_rxa == 0)
rx_error |= Z180_STAT_FE;
if (m_asci_cntlb & Z180_CNTLB_MP)
{
m_asci_cntla |= ((m_rsr >> stop_bits) & 1) ? Z180_CNTLA_MPBR_EFR : 0;
m_asci_cntla |= ((m_rsr >> data_bits) & 1) ? Z180_CNTLA_MPBR_EFR : 0;
}
else if (m_asci_cntla & Z180_CNTLA_MODE_PARITY)
{
uint8_t parity = 0;
for (int i = 0; i < ((m_asci_cntla & Z180_CNTLA_MODE_DATA) ? 8 : 7); i++)
for (int i = 0; i < data_bits; i++)
parity ^= BIT(m_rsr, i);
if (m_asci_cntlb & Z180_CNTLB_PEO) parity ^= 1; // odd parity
if (((m_rsr >> stop_bits) & 1) != parity)
if (((m_rsr >> data_bits) & 1) != parity)
rx_error |= Z180_STAT_PE;
}
// Skip only if MPE mode active and MPB is 0
if (!((m_asci_cntla & Z180_CNTLA_MPE) && ((m_asci_cntla & Z180_CNTLA_MPBR_EFR) == 0)))
{
LOG("%s: %X received%s%s\n", machine().time().to_string(), m_rsr, (rx_error & Z180_STAT_FE) ? " (framing error)" : "", (rx_error & Z180_STAT_PE) ? " (bad parity)" : "");
set_fifo_data(m_rsr, rx_error);
}
}