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i8251: as per the manual, disabling Tx mid-byte should wait for transmission to finish [R. Belmont]

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This commit is contained in:
R. Belmont 2014-01-10 03:09:04 +00:00
parent 14cd942836
commit 0c310baef5
2 changed files with 45 additions and 15 deletions
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59
src/emu/machine/i8251.c
View File

@ -172,13 +172,13 @@ void i8251_device::transmit_clock()
else
return;
/* transmit enable? */
/* transmit enabled? */
if (m_command & (1<<0))
{
/* transmit register full? */
/* do we have a character to send? */
if ((m_status & I8251_STATUS_TX_READY)==0)
{
/* if transmit reg is empty */
/* is diserial ready for it? */
if (is_transmit_register_empty())
{
/* set it up */
@ -193,18 +193,32 @@ void i8251_device::transmit_clock()
}
}
/* if transmit is not empty... transmit data */
/* if diserial has bits to send, make them so */
if (!is_transmit_register_empty())
{
UINT8 data = transmit_register_get_data_bit();
// logerror("I8251\n");
//transmit_register_send_bit();
m_tx_busy = true;
m_out_txd_func(data);
m_connection_state &= ~TX;
m_connection_state|=(data<<5);
serial_connection_out();
}
// is transmitter totally done?
if ((m_status & I8251_STATUS_TX_READY) && is_transmit_register_empty())
{
m_tx_busy = false;
if (m_disable_tx_pending)
{
LOG(("Applying pending disable\n"));
m_disable_tx_pending = false;
m_command &= ~(1<<0);
set_out_data_bit(1);
update_tx_ready();
}
}
}
#if 0
@ -325,6 +339,7 @@ void i8251_device::device_reset()
m_data = 0;
m_rxc = m_txc = 0;
m_br_factor = 1;
m_tx_busy = m_disable_tx_pending = false;
/* update tx empty pin output */
update_tx_empty();
@ -584,10 +599,30 @@ WRITE8_MEMBER(i8251_device::control_w)
if (data & (1<<0))
{
LOG(("transmit enable\n"));
/* if we get a tx enable with a disable pending, cancel the disable */
m_disable_tx_pending = false;
}
else
{
LOG(("transmit disable\n"));
if (m_tx_busy)
{
if (!m_disable_tx_pending)
{
LOG(("Tx busy, set pending disable\n"));
}
m_disable_tx_pending = true;
m_command |= (1<<0);
}
else
{
LOG(("transmit disable\n"));
if ((data & (1<<0))==0)
{
/* held in high state when transmit disable */
set_out_data_bit(1);
}
}
}
@ -630,12 +665,6 @@ WRITE8_MEMBER(i8251_device::control_w)
m_connection_state |= DTR;
}
if ((data & (1<<0))==0)
{
/* held in high state when transmit disable */
set_out_data_bit(1);
}
/* refresh outputs */
serial_connection_out();
@ -684,7 +713,7 @@ WRITE8_MEMBER(i8251_device::data_w)
{
m_data = data;
//logerror("write data: %02x\n",data);
// printf("i8251 transmit char: %02x\n",data);
/* writing clears */
m_status &=~I8251_STATUS_TX_READY;
@ -705,7 +734,7 @@ WRITE8_MEMBER(i8251_device::data_w)
void i8251_device::receive_character(UINT8 ch)
{
//logerror("i8251 receive char: %02x\n",ch);
// printf("i8251 receive char: %02x\n",ch);
m_data = ch;

1
src/emu/machine/i8251.h
View File

@ -129,6 +129,7 @@ private:
/* data being received */
UINT8 m_data;
bool m_tx_busy, m_disable_tx_pending;
};
// device type definition