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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
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@ -172,13 +172,13 @@ void i8251_device::transmit_clock()
else else
return; return;
/* transmit enable? */ /* transmit enabled? */
if (m_command & (1<<0)) if (m_command & (1<<0))
{ {
/* transmit register full? */ /* do we have a character to send? */
if ((m_status & I8251_STATUS_TX_READY)==0) if ((m_status & I8251_STATUS_TX_READY)==0)
{ {
/* if transmit reg is empty */ /* is diserial ready for it? */
if (is_transmit_register_empty()) if (is_transmit_register_empty())
{ {
/* set it up */ /* 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()) if (!is_transmit_register_empty())
{ {
UINT8 data = transmit_register_get_data_bit(); UINT8 data = transmit_register_get_data_bit();
// logerror("I8251\n"); m_tx_busy = true;
//transmit_register_send_bit();
m_out_txd_func(data); m_out_txd_func(data);
m_connection_state &= ~TX; m_connection_state &= ~TX;
m_connection_state|=(data<<5); m_connection_state|=(data<<5);
serial_connection_out(); 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 #if 0
@ -325,6 +339,7 @@ void i8251_device::device_reset()
m_data = 0; m_data = 0;
m_rxc = m_txc = 0; m_rxc = m_txc = 0;
m_br_factor = 1; m_br_factor = 1;
m_tx_busy = m_disable_tx_pending = false;
/* update tx empty pin output */ /* update tx empty pin output */
update_tx_empty(); update_tx_empty();
@ -584,10 +599,30 @@ WRITE8_MEMBER(i8251_device::control_w)
if (data & (1<<0)) if (data & (1<<0))
{ {
LOG(("transmit enable\n")); LOG(("transmit enable\n"));
/* if we get a tx enable with a disable pending, cancel the disable */
m_disable_tx_pending = false;
} }
else 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; m_connection_state |= DTR;
} }
if ((data & (1<<0))==0)
{
/* held in high state when transmit disable */
set_out_data_bit(1);
}
/* refresh outputs */ /* refresh outputs */
serial_connection_out(); serial_connection_out();
@ -684,7 +713,7 @@ WRITE8_MEMBER(i8251_device::data_w)
{ {
m_data = data; m_data = data;
//logerror("write data: %02x\n",data); // printf("i8251 transmit char: %02x\n",data);
/* writing clears */ /* writing clears */
m_status &=~I8251_STATUS_TX_READY; m_status &=~I8251_STATUS_TX_READY;
@ -705,7 +734,7 @@ WRITE8_MEMBER(i8251_device::data_w)
void i8251_device::receive_character(UINT8 ch) void i8251_device::receive_character(UINT8 ch)
{ {
//logerror("i8251 receive char: %02x\n",ch); // printf("i8251 receive char: %02x\n",ch);
m_data = ch; m_data = ch;

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

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