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mc68681: separate transmitter holding and shift registers

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This commit is contained in:
Patrick Mackinlay 2023-06-07 08:56:44 +07:00
parent 8076c9a8f5
commit 6b3ba498ed
2 changed files with 18 additions and 43 deletions
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59
src/devices/machine/mc68681.cpp
View File

@ -1168,7 +1168,6 @@ duart_channel::duart_channel(const machine_config &mconfig, const char *tag, dev
, SR(0)
, rx_enabled(0)
, rx_fifo_num(0)
, tx_enabled(0)
, m_tx_break(false)
{
std::fill_n(&rx_fifo[0], MC68681_RX_FIFO_SIZE + 1, 0);
@ -1192,9 +1191,7 @@ void duart_channel::device_start()
save_item(NAME(rx_fifo_read_ptr));
save_item(NAME(rx_fifo_write_ptr));
save_item(NAME(rx_fifo_num));
save_item(NAME(tx_enabled));
save_item(NAME(tx_data));
save_item(NAME(tx_ready));
save_item(NAME(m_tx_break));
}
@ -1267,19 +1264,11 @@ void duart_channel::rx_fifo_push(uint8_t data, uint8_t errors)
void duart_channel::tra_complete()
{
//printf("%s ch %d Tx complete\n", tag(), m_ch);
tx_ready = 1;
if (!(SR & STATUS_TRANSMITTER_EMPTY))
transmit_register_setup(tx_data);
SR |= STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY;
if (m_ch == 0)
m_uart->set_ISR_bits(INT_TXRDYA);
else
m_uart->set_ISR_bits(INT_TXRDYB);
// if local loopback is on, write the transmitted data as if a byte had been received
if ((MR2 & 0xc0) == 0x80)
rx_fifo_push(tx_data, 0);
update_interrupts();
}
@ -1307,10 +1296,9 @@ void duart_channel::tra_callback()
m_uart->write_d_tx(bit);
}
}
else // must call this to advance the transmitter
{
transmit_register_get_data_bit();
}
else
// loop back transmitted bit
rx_w(transmit_register_get_data_bit());
}
void duart_channel::update_interrupts()
@ -1559,8 +1547,6 @@ void duart_channel::write_CR(uint8_t data)
receive_register_reset();
break;
case 3: /* Reset channel transmitter */
tx_enabled = 0;
tx_ready = 0;
SR &= ~(STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY);
if (m_ch == 0)
m_uart->clear_ISR_bits(INT_TXRDYA);
@ -1622,10 +1608,8 @@ void duart_channel::write_CR(uint8_t data)
SR &= ~STATUS_RECEIVER_READY;
}
if (!tx_enabled && BIT(data, 2))
if (!(SR & STATUS_TRANSMITTER_READY) && BIT(data, 2))
{
tx_enabled = 1;
tx_ready = 1;
SR |= STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY;
if (m_ch == 0)
m_uart->set_ISR_bits(INT_TXRDYA);
@ -1634,8 +1618,6 @@ void duart_channel::write_CR(uint8_t data)
}
if (BIT(data, 3))
{
tx_enabled = 0;
tx_ready = 0;
SR &= ~(STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY);
if (m_ch == 0)
m_uart->clear_ISR_bits(INT_TXRDYA);
@ -1648,25 +1630,20 @@ void duart_channel::write_CR(uint8_t data)
void duart_channel::write_TX(uint8_t data)
{
tx_data = data;
if (!(SR & STATUS_TRANSMITTER_READY))
{
logerror("write_tx transmitter not ready (data 0x%02x discarded)\n", data);
return;
}
/* if (!tx_ready)
{
printf("Write %02x to TX when TX not ready!\n", data);
}*/
if (!is_transmit_register_empty())
{
SR &= ~(STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY);
//printf("%s ch %d Tx %c [%02x]\n", tag(), m_ch, isprint(data) ? data : ' ', data);
tx_ready = 0;
SR &= ~(STATUS_TRANSMITTER_READY | STATUS_TRANSMITTER_EMPTY);
if (m_ch == 0)
m_uart->clear_ISR_bits(INT_TXRDYA);
tx_data = data;
}
else
m_uart->clear_ISR_bits(INT_TXRDYB);
// send tx_data
transmit_register_setup(tx_data);
transmit_register_setup(data);
update_interrupts();
}

2
src/devices/machine/mc68681.h
View File

@ -71,9 +71,7 @@ private:
int m_ch;
/* Transmitter */
uint8_t tx_enabled;
uint8_t tx_data;
uint8_t tx_ready;
bool m_tx_break;
/* Rx/Tx clocking */