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Merge pull request #448 from fulivi/i8251_fix
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Fix for i8251 device driver
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@rb6502
rb6502 committed Oct 31, 2015
2 parents c7c515f + d970816 commit 518a33c
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Showing 2 changed files with 68 additions and 90 deletions.
146 changes: 60 additions & 86 deletions src/devices/machine/i8251.c
View file
Expand Up @@ -109,8 +109,6 @@ void i8251_device::device_start()
save_item(NAME(m_br_factor));
save_item(NAME(m_rx_data));
save_item(NAME(m_tx_data));
save_item(NAME(m_tx_busy));
save_item(NAME(m_disable_tx_pending));
device_serial_interface::register_save_state(machine().save(), this);
}

Expand Down Expand Up @@ -166,7 +164,33 @@ void i8251_device::receive_clock()
}
}

/*-------------------------------------------------
is_tx_enabled
-------------------------------------------------*/
bool i8251_device::is_tx_enabled(void) const
{
return BIT(m_command , 0) != 0 && m_cts == 0;
}

/*-------------------------------------------------
check_for_tx_start
-------------------------------------------------*/
void i8251_device::check_for_tx_start(void)
{
if (is_tx_enabled() && (m_status & (I8251_STATUS_TX_EMPTY | I8251_STATUS_TX_READY)) == I8251_STATUS_TX_EMPTY) {
start_tx();
}
}

/*-------------------------------------------------
start_tx
-------------------------------------------------*/
void i8251_device::start_tx(void)
{
transmit_register_setup(m_tx_data);
m_status &= ~I8251_STATUS_TX_EMPTY;
m_status |= I8251_STATUS_TX_READY;
}

/*-------------------------------------------------
transmit_clock
Expand All @@ -181,50 +205,21 @@ void i8251_device::transmit_clock()
else
return;

/* transmit enabled? */
if (m_command & (1<<0))
{
/* do we have a character to send? */
if ((m_status & I8251_STATUS_TX_READY)==0)
{
/* is diserial ready for it? */
if (is_transmit_register_empty())
{
/* set it up */
transmit_register_setup(m_tx_data);
/* i8251 transmit reg now empty */
m_status |=I8251_STATUS_TX_EMPTY;
/* ready for next transmit */
m_status |=I8251_STATUS_TX_READY;

update_tx_empty();
update_tx_ready();
}
}

/* if diserial has bits to send, make them so */
if (!is_transmit_register_empty())
{
UINT8 data = transmit_register_get_data_bit();
m_tx_busy = true;
m_txd_handler(data);
}

// 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);
m_txd_handler(1);
update_tx_ready();
}
}
}
if (is_transmit_register_empty()) {
if ((m_status & I8251_STATUS_TX_READY) == 0 && (is_tx_enabled() || (m_flags & I8251_DELAYED_TX_EN) != 0)) {
start_tx();
} else {
m_status |= I8251_STATUS_TX_EMPTY;
}
update_tx_ready();
update_tx_empty();
}
/* if diserial has bits to send, make them so */
if (!is_transmit_register_empty())
{
UINT8 data = transmit_register_get_data_bit();
m_txd_handler(data);
}

#if 0
/* hunt mode? */
Expand Down Expand Up @@ -271,21 +266,7 @@ void i8251_device::update_tx_ready()
Transmit enable is 1
*/

tx_ready = 0;

/* transmit enable? */
if ((m_command & (1<<0))!=0)
{
/* other side has rts set (comes in as CTS at this side) */
if (!m_cts)
{
if (m_status & I8251_STATUS_TX_EMPTY)
{
/* enable transfer */
tx_ready = 1;
}
}
}
tx_ready = is_tx_enabled() && (m_status & I8251_STATUS_TX_READY) != 0;

m_txrdy_handler(tx_ready);
}
Expand Down Expand Up @@ -344,7 +325,6 @@ void i8251_device::device_reset()
m_tx_data = 0;
m_rxc_count = m_txc_count = 0;
m_br_factor = 1;
m_tx_busy = m_disable_tx_pending = false;

/* update tx empty pin output */
update_tx_empty();
Expand Down Expand Up @@ -404,30 +384,10 @@ WRITE8_MEMBER(i8251_device::command_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
{
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 */
m_txd_handler(1);
}
}
LOG(("transmit disable\n"));
}


Expand Down Expand Up @@ -473,8 +433,10 @@ WRITE8_MEMBER(i8251_device::command_w)
m_flags |= I8251_EXPECTING_MODE;
}

check_for_tx_start();
update_rx_ready();
update_tx_ready();
update_tx_empty();
}

WRITE8_MEMBER(i8251_device::mode_w)
Expand Down Expand Up @@ -692,12 +654,20 @@ WRITE8_MEMBER(i8251_device::data_w)
{
m_tx_data = data;

LOG(("data_w %02x\n" , data));
// printf("i8251 transmit char: %02x\n",data);
LOG(("data_w %02x\n" , data));

/* writing clears */
m_status &=~I8251_STATUS_TX_READY;
m_status &=~I8251_STATUS_TX_EMPTY;
update_tx_ready();

// Store state of tx enable when writing to DB buffer
if (is_tx_enabled()) {
m_flags |= I8251_DELAYED_TX_EN;
} else {
m_flags &= ~I8251_DELAYED_TX_EN;
}

check_for_tx_start();

/* if transmitter is active, then tx empty will be signalled */

Expand Down Expand Up @@ -758,6 +728,10 @@ WRITE_LINE_MEMBER(i8251_device::write_rxd)
WRITE_LINE_MEMBER(i8251_device::write_cts)
{
m_cts = state;

check_for_tx_start();
update_tx_ready();
update_tx_empty();
}

WRITE_LINE_MEMBER(i8251_device::write_dsr)
Expand Down
12 changes: 8 additions & 4 deletions src/devices/machine/i8251.h
View file
Expand Up @@ -92,11 +92,16 @@ class i8251_device : public device_t,
void update_tx_empty();
void transmit_clock();
void receive_clock();
bool is_tx_enabled(void) const;
void check_for_tx_start(void);
void start_tx(void);


enum
{
I8251_EXPECTING_MODE = 0x01,
I8251_EXPECTING_SYNC_BYTE = 0x02
I8251_EXPECTING_SYNC_BYTE = 0x02,
I8251_DELAYED_TX_EN = 0x04
};

private:
Expand Down Expand Up @@ -133,9 +138,8 @@ class i8251_device : public device_t,

/* data being received */
UINT8 m_rx_data;
UINT8 m_tx_data;
bool m_tx_busy;
bool m_disable_tx_pending;
/* tx buffer */
UINT8 m_tx_data;
};

class v53_scu_device : public i8251_device
Expand Down

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