mame/src/devices/machine/i8251.cpp
2019-09-26 13:51:13 +02:00

923 lines
20 KiB
C++

// license:BSD-3-Clause
// copyright-holders:smf, Robbbert
/*********************************************************************
i8251.cpp
Intel 8251 Universal Synchronous/Asynchronous Receiver Transmitter code
NEC uPD71051 is a clone
The V53/V53A use a customized version with only the Asynchronous mode
and a split command / mode register
To Do:
- BRKDET: if, in Async mode, 16 low RxD bits in succession are clocked in,
the SYNDET pin & status must go high. It will go low upon a
status read, same as what happens with sync.
- SYNC/BISYNC with PARITY is not tested, and therefore possibly buggy.
*********************************************************************/
#include "emu.h"
#include "i8251.h"
#define LOG_STAT (1U << 1)
#define LOG_COM (1U << 2)
#define LOG_MODE (1U << 3)
#define LOG_BITS (1U << 4)
//#define VERBOSE (LOG_BITS|LOG_GENERAL)
//#define LOG_OUTPUT_STREAM std::cout
#include "logmacro.h"
#define LOGSTAT(...) LOGMASKED(LOG_STAT, __VA_ARGS__)
#define LOGCOM(...) LOGMASKED(LOG_COM, __VA_ARGS__)
#define LOGMODE(...) LOGMASKED(LOG_MODE, __VA_ARGS__)
#define LOGBITS(...) LOGMASKED(LOG_BITS, __VA_ARGS__)
//**************************************************************************
// DEVICE DEFINITIONS
//**************************************************************************
DEFINE_DEVICE_TYPE(I8251, i8251_device, "i8251", "Intel 8251 USART")
DEFINE_DEVICE_TYPE(V5X_SCU, v5x_scu_device, "v5x_scu", "NEC V5X SCU")
//-------------------------------------------------
// i8251_device - constructor
//-------------------------------------------------
i8251_device::i8251_device(
const machine_config &mconfig,
device_type type,
const char *tag,
device_t *owner,
uint32_t clock)
: device_t(mconfig, type, tag, owner, clock),
device_serial_interface(mconfig, *this),
m_txd_handler(*this),
m_dtr_handler(*this),
m_rts_handler(*this),
m_rxrdy_handler(*this),
m_txrdy_handler(*this),
m_txempty_handler(*this),
m_syndet_handler(*this),
m_cts(1),
m_dsr(1),
m_rxd(0),
m_rxc(0),
m_txc(0)
{
}
i8251_device::i8251_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: i8251_device(mconfig, I8251, tag, owner, clock)
{
}
v5x_scu_device::v5x_scu_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: i8251_device(mconfig, V5X_SCU, tag, owner, clock)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void i8251_device::device_start()
{
// resolve callbacks
m_txd_handler.resolve_safe();
m_rts_handler.resolve_safe();
m_dtr_handler.resolve_safe();
m_rxrdy_handler.resolve_safe();
m_txrdy_handler.resolve_safe();
m_txempty_handler.resolve_safe();
m_syndet_handler.resolve_safe();
save_item(NAME(m_flags));
save_item(NAME(m_sync_byte_count));
save_item(NAME(m_status));
save_item(NAME(m_command));
save_item(NAME(m_mode_byte));
save_item(NAME(m_delayed_tx_en));
save_item(NAME(m_sync1));
save_item(NAME(m_sync2));
save_item(NAME(m_sync8));
save_item(NAME(m_sync16));
save_item(NAME(m_cts));
save_item(NAME(m_dsr));
save_item(NAME(m_rxd));
save_item(NAME(m_rxc));
save_item(NAME(m_txc));
save_item(NAME(m_rxc_count));
save_item(NAME(m_txc_count));
save_item(NAME(m_br_factor));
save_item(NAME(m_rx_data));
save_item(NAME(m_tx_data));
save_item(NAME(m_syndet_pin));
save_item(NAME(m_hunt_on));
save_item(NAME(m_ext_syn_set));
save_item(NAME(m_rxd_bits));
save_item(NAME(m_data_bits_count));
}
/*-------------------------------------------------
update_rx_ready
-------------------------------------------------*/
void i8251_device::update_rx_ready()
{
int state = m_status & I8251_STATUS_RX_READY;
// masked?
if (!BIT(m_command, 2))
state = 0;
m_rxrdy_handler(state != 0);
}
/*-------------------------------------------------
receive_clock
-------------------------------------------------*/
void i8251_device::receive_clock()
{
/* receive enable? */
if (BIT(m_command, 2))
{
const bool sync = is_receive_register_synchronized();
if (sync)
{
--m_rxc_count;
if (m_rxc_count)
return;
}
//logerror("I8251\n");
/* get bit received from other side and update receive register */
//LOGBITS("8251: Rx Sampled %d\n", m_rxd);
receive_register_update_bit(m_rxd);
if (is_receive_register_synchronized())
m_rxc_count = sync ? m_br_factor : (3 * m_br_factor / 2);
if (is_receive_register_full())
{
receive_register_extract();
if (is_receive_parity_error())
m_status |= I8251_STATUS_PARITY_ERROR;
if (is_receive_framing_error())
m_status |= I8251_STATUS_FRAMING_ERROR;
receive_character(get_received_char());
}
}
}
bool i8251_device::calc_parity(u8 ch)
{
bool data = 0;
for (u8 b = 0; b < 8; b++)
data ^= BIT(ch, b);
return data;
}
void i8251_device::sync1_rxc()
{
// is rx enabled?
if (!BIT(m_command, 2))
return;
// if ext sync, and syndet low, quit
// Todo: what should happen here?
if (m_syndet_pin && !m_ext_syn_set)
return;
u8 need_parity = BIT(m_mode_byte, 4);
// see about parity
if (need_parity && (m_rxd_bits == m_data_bits_count))
{
if (calc_parity(m_sync1) != m_rxd)
m_status |= I8251_STATUS_PARITY_ERROR;
// and then continue on as if everything was ok
}
else
{
// add bit to byte
m_sync1 = (m_sync1 >> 1) | (m_rxd << (m_data_bits_count-1));
}
// if we are in hunt mode, the byte loaded has to
// be the sync byte. If not, go around again.
// if we leave hunt mode now, the sync byte must not go to the receive buffer
bool was_in_hunt_mode = false;
if (m_hunt_on)
{
if (m_sync1 == m_sync8)
{
m_rxd_bits = m_data_bits_count;
m_hunt_on = false;
was_in_hunt_mode = true;
}
else
return;
}
// is byte complete? if not, quit
m_rxd_bits++;
if (m_rxd_bits < (m_data_bits_count + need_parity))
return;
// now we have a synchronised byte, and parity has been dealt with
// copy byte to rx buffer
if (!was_in_hunt_mode)
receive_character(m_sync1);
// Is it a sync byte? syndet gets indicated whenever
// a sync byte passes by, regardless of hunt_mode status.
if (m_sync1 == m_sync8)
update_syndet(true);
m_rxd_bits = 0;
m_sync1 = 0;
}
void i8251_device::sync2_rxc()
{
// is rx enabled?
if (!BIT(m_command, 2))
return;
// if ext sync, and syndet low, quit
if (m_syndet_pin && !m_ext_syn_set)
return;
u8 need_parity = BIT(m_mode_byte, 4);
// see about parity
if (need_parity && (m_rxd_bits == m_data_bits_count))
{
if (calc_parity(m_sync1) != m_rxd)
m_status |= I8251_STATUS_PARITY_ERROR;
// and then continue on as if everything was ok
}
else
{
// add bit to byte
m_sync1 = (m_sync1 >> 1) | (m_rxd << (m_data_bits_count-1));
m_sync2 = (m_sync2 >> 1) | (m_rxd << (m_data_bits_count*2-1));
}
// if we are in hunt mode, the byte loaded has to
// be the sync byte. If not, go around again.
// if we leave hunt mode now, the sync byte must not go to the receive buffer
bool was_in_hunt_mode = false;
if (m_hunt_on)
{
if (m_sync2 == m_sync16)
{
m_rxd_bits = m_data_bits_count;
m_hunt_on = false;
was_in_hunt_mode = true;
}
else
return;
}
// is byte complete? if not, quit
m_rxd_bits++;
if (m_rxd_bits < (m_data_bits_count + need_parity))
return;
// now we have a synchronised byte, and parity has been dealt with
// copy byte to rx buffer
if (!was_in_hunt_mode)
receive_character(m_sync1);
// Is it a sync byte? syndet gets indicated whenever
// a sync byte passes by, regardless of hunt_mode status.
if (m_sync2 == m_sync16)
update_syndet(true);
m_rxd_bits = 0;
m_sync1 = 0;
m_sync2 = 0;
}
/*-------------------------------------------------
is_tx_enabled
-------------------------------------------------*/
bool i8251_device::is_tx_enabled() const
{
return BIT(m_command, 0) && !m_cts;
}
/*-------------------------------------------------
check_for_tx_start
-------------------------------------------------*/
void i8251_device::check_for_tx_start()
{
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()
{
LOG("start_tx %02x\n", m_tx_data);
transmit_register_setup(m_tx_data);
m_status &= ~I8251_STATUS_TX_EMPTY;
m_status |= I8251_STATUS_TX_READY;
}
/*-------------------------------------------------
transmit_clock
-------------------------------------------------*/
void i8251_device::transmit_clock()
{
m_txc_count++;
if (m_txc_count != m_br_factor)
return;
m_txc_count = 0;
if (is_transmit_register_empty())
{
if ((m_status & I8251_STATUS_TX_READY) == 0 && (is_tx_enabled() || m_delayed_tx_en))
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_t data = transmit_register_get_data_bit();
LOGBITS("8251: Tx Present a %d\n", data);
m_txd_handler(data);
}
}
/*-------------------------------------------------
update_tx_ready
-------------------------------------------------*/
void i8251_device::update_tx_ready()
{
/* clear tx ready state */
int tx_ready;
/* tx ready output is set if:
DB Buffer Empty &
CTS is set &
Transmit enable is 1
*/
tx_ready = is_tx_enabled() && (m_status & I8251_STATUS_TX_READY) != 0;
m_txrdy_handler(tx_ready);
}
/*-------------------------------------------------
update_tx_empty
-------------------------------------------------*/
void i8251_device::update_tx_empty()
{
if (m_status & I8251_STATUS_TX_EMPTY)
{
// return TxD to marking state (high) if not sending break character
m_txd_handler(!BIT(m_command, 3));
}
m_txempty_handler((m_status & I8251_STATUS_TX_EMPTY) != 0);
}
/*---------------------------------------------------
update_syndet - indicates that a sync
character string has been received
1 = valid sync; 0 = hunt mode on, or status read
-----------------------------------------------------*/
void i8251_device::update_syndet(bool voltage)
{
LOG("I8251: Syndet %d\n",voltage);
// Sanity check
if (voltage && m_hunt_on)
printf("I8251: Syndet - invalid parameters\n");
// Adjust status register
if (voltage)
m_status |= 0x40;
else
m_status &= ~0x40;
// If syndet is set as an output pin, indicate new status
if (!m_syndet_pin)
m_syndet_handler(voltage);
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void i8251_device::device_reset()
{
LOG("I8251: Reset\n");
/* what is the default setup when the 8251 has been reset??? */
/* i8251 datasheet explains the state of tx pin at reset */
/* tx is set to 1 */
m_txd_handler(1);
/* assumption */
m_rts_handler(1);
m_dtr_handler(1);
transmit_register_reset();
receive_register_reset();
/* expecting mode byte */
m_flags = I8251_NEXT_MODE;
/* no character to read by cpu */
/* transmitter is ready and is empty */
m_status = I8251_STATUS_TX_EMPTY | I8251_STATUS_TX_READY;
LOGSTAT("status is reset to %02x\n", m_status);
m_mode_byte = 0;
m_command = 0;
m_rx_data = 0;
m_tx_data = 0;
m_rxc_count = m_txc_count = 0;
m_br_factor = 1;
/* update tx empty pin output */
update_tx_empty();
/* update rx ready pin output */
update_rx_ready();
/* update tx ready pin output */
update_tx_ready();
}
/*-------------------------------------------------
control_w
-------------------------------------------------*/
void i8251_device::command_w(uint8_t data)
{
/* command */
m_command = data;
LOG("I8251: Command byte: %02x\n", data);
LOGCOM(" Tx enable: %d\n", data & 0x01 ? 1 : 0); // bit 0: 0 = transmit disable 1 = transmit enable
LOGCOM(" DTR : %d\n", data & 0x02 ? 1 : 0); // bit 1: 0 = /DTR set to 1 1 = /DTR set to 0
LOGCOM(" Rx enable: %d\n", data & 0x04 ? 1 : 0); // bit 2: 0 = receive disable 1 = receive enable
LOGCOM(" Send BRK : %d\n", data & 0x08 ? 1 : 0); // bit 3: 0 = normal operation 1 = send break character
LOGCOM(" Err reset: %d\n", data & 0x10 ? 1 : 0); // bit 4: 0 = normal operation 1 = reset error flag
LOGCOM(" RTS : %d\n", data & 0x20 ? 1 : 0); // bit 5: 0 = /RTS set to 1 1 = /RTS set to 0
LOGCOM(" Reset : %d\n", data & 0x40 ? 1 : 0); // bit 6: 0 = normal operation 1 = internal reset
LOGCOM(" Hunt mode: %d\n", data & 0x80 ? 1 : 0); // bit 7: 0 = normal operation 1 = hunt mode
m_rts_handler(!BIT(data, 5));
m_dtr_handler(!BIT(data, 1));
if (BIT(data, 4))
{
LOGSTAT("status errors are reset\n");
m_status &= ~(I8251_STATUS_PARITY_ERROR | I8251_STATUS_OVERRUN_ERROR | I8251_STATUS_FRAMING_ERROR);
}
if (BIT(data, 6))
{
// datasheet says "returns to mode format", not
// completely resets the chip. behavior of DEC Rainbow
// backs this up.
m_flags = I8251_NEXT_MODE;
}
// Hunt mode
m_hunt_on = false;
update_syndet(false);
if (m_sync_byte_count)
m_hunt_on = BIT(data, 7);
if (m_hunt_on)
m_ext_syn_set = false;
if (BIT(data, 3))
m_txd_handler(0);
check_for_tx_start();
update_rx_ready();
update_tx_ready();
update_tx_empty();
}
void i8251_device::mode_w(uint8_t data)
{
LOG("I8251: Mode byte = %02X\n", data);
m_mode_byte = data;
/* Asynchronous
bit 7,6: stop bit length
0 = inhibit
1 = 1 bit
2 = 1.5 bits
3 = 2 bits
bit 5: parity type
0 = parity odd
1 = parity even
bit 4: parity test enable
0 = disable
1 = enable
bit 3,2: character length
0 = 5 bits
1 = 6 bits
2 = 7 bits
3 = 8 bits
bit 1,0: baud rate factor
0 = defines command byte for synchronous or asynchronous
1 = x1
2 = x16
3 = x64
Synchronous
bit 7: Number of sync characters
0 = 1 character
1 = 2 character
bit 6: Synchronous mode
0 = Internal synchronisation
1 = External synchronisation
bit 5: parity type
0 = parity odd
1 = parity even
bit 4: parity test enable
0 = disable
1 = enable
bit 3,2: character length
0 = 5 bits
1 = 6 bits
2 = 7 bits
3 = 8 bits
bit 1,0 = 0
*/
m_data_bits_count = ((data >> 2) & 0x03) + 5;
LOG("Character length: %d\n", m_data_bits_count);
parity_t parity = PARITY_NONE;
switch (data & 0x30)
{
case 0x10:
LOG("Enable ODD parity checking.\n");
parity = PARITY_ODD;
break;
case 0x30:
LOG("Enable EVEN parity checking.\n");
parity = PARITY_EVEN;
break;
default:
LOG("Disable parity check.\n");
}
stop_bits_t stop_bits = STOP_BITS_0;
m_br_factor = 1;
m_flags = I8251_NEXT_COMMAND;
m_sync_byte_count = 0;
m_syndet_pin = false;
/* Synchronous or Asynchronous? */
if (data & 0x03)
{
LOG("I8251: Asynchronous operation\n");
switch (data & 0xc0)
{
case 0x40:
stop_bits = STOP_BITS_1;
LOG("stop bit: 1 bit\n");
break;
case 0x80:
stop_bits = STOP_BITS_1_5;
LOG("stop bit: 1.5 bits\n");
break;
case 0xc0:
stop_bits = STOP_BITS_2;
LOG("stop bit: 2 bits\n");
break;
default:
LOG("stop bit: inhibit\n");
break;
}
set_data_frame(1, m_data_bits_count, parity, stop_bits);
switch (data & 0x03)
{
case 2:
m_br_factor = 16;
break;
case 3:
m_br_factor = 64;
break;
}
}
else
{
LOG("I8251: Synchronous operation\n");
/* setup for sync byte(s) */
m_flags = BIT(data, 7) ? I8251_NEXT_SYNC2 : I8251_NEXT_SYNC1;
m_sync_byte_count = BIT(data, 7) ? 1 : 2;
set_data_frame(0, m_data_bits_count, parity, stop_bits);
m_syndet_pin = BIT(data, 6);
m_sync8 = 0;
m_sync16 = 0;
m_rxd_bits = 0;
m_sync1 = 0;
}
receive_register_reset();
m_txc_count = 0;
}
void i8251_device::sync1_w(uint8_t data)
{
m_sync16 = (data << 8);
m_flags = I8251_NEXT_SYNC2;
}
void i8251_device::sync2_w(uint8_t data)
{
if (m_sync_byte_count == 2)
m_sync16 |= data;
else
m_sync8 = data;
m_flags = I8251_NEXT_COMMAND;
}
void i8251_device::control_w(uint8_t data)
{
if (m_flags == I8251_NEXT_SYNC1)
sync1_w(data);
else
if (m_flags == I8251_NEXT_SYNC2)
sync2_w(data);
else
if (m_flags == I8251_NEXT_MODE)
mode_w(data);
else
command_w(data);
}
/*-------------------------------------------------
status_r
-------------------------------------------------*/
uint8_t i8251_device::status_r()
{
uint8_t status = (m_dsr << 7) | m_status;
LOG("status: %02x\n", status);
// Syndet always goes off after status read
update_syndet(false);
return status;
}
/*-------------------------------------------------
data_w
-------------------------------------------------*/
void i8251_device::data_w(uint8_t data)
{
m_tx_data = data;
LOG("data_w %02x\n", data);
/* writing clears */
m_status &=~I8251_STATUS_TX_READY;
LOGSTAT("8251: status cleared TX_READY by data_w\n");
update_tx_ready();
// Store state of tx enable when writing to DB buffer
m_delayed_tx_en = is_tx_enabled();
check_for_tx_start();
/* if transmitter is active, then tx empty will be signalled */
update_tx_ready();
update_tx_empty();
}
/*-------------------------------------------------
receive_character - called when last
bit of data has been received
-------------------------------------------------*/
void i8251_device::receive_character(uint8_t ch)
{
LOG("receive_character %02x\n", ch);
m_rx_data = ch;
LOGSTAT("status RX READY test %02x\n", m_status);
/* char has not been read and another has arrived! */
if (m_status & I8251_STATUS_RX_READY)
{
m_status |= I8251_STATUS_OVERRUN_ERROR;
LOGSTAT("status overrun set\n");
}
LOGSTAT("status pre RX READY set %02x\n", m_status);
m_status |= I8251_STATUS_RX_READY;
LOGSTAT("status post RX READY set %02x\n", m_status);
update_rx_ready();
}
/*-------------------------------------------------
data_r - read data
-------------------------------------------------*/
uint8_t i8251_device::data_r()
{
LOG("read data: %02x, STATUS=%02x\n",m_rx_data,m_status);
/* reading clears */
if (!machine().side_effects_disabled())
{
m_status &= ~I8251_STATUS_RX_READY;
LOGSTAT("status RX_READY cleared\n");
update_rx_ready();
}
return m_rx_data;
}
uint8_t i8251_device::read(offs_t offset)
{
if (offset)
return status_r();
else
return data_r();
}
void i8251_device::write(offs_t offset, uint8_t data)
{
if (offset)
control_w(data);
else
data_w(data);
}
WRITE_LINE_MEMBER(i8251_device::write_rxd)
{
m_rxd = state;
LOGBITS("8251: Presented a %d\n", m_rxd);
// device_serial_interface::rx_w(state);
}
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)
{
m_dsr = !state;
}
WRITE_LINE_MEMBER(i8251_device::write_rxc)
{
if (!m_rxc && state)
{
if (m_sync_byte_count == 1)
sync1_rxc();
else
if (m_sync_byte_count == 2)
sync2_rxc();
else
receive_clock();
}
m_rxc = state;
}
WRITE_LINE_MEMBER(i8251_device::write_txc)
{
if (m_txc != state)
{
m_txc = state;
if (!m_txc)
transmit_clock();
}
}
// forcibly kill hunt mode
WRITE_LINE_MEMBER(i8251_device::write_syn)
{
if (m_syndet_pin && state) // must be set as input
{
m_ext_syn_set = true;
m_hunt_on = false;
update_syndet(true);
}
}
READ_LINE_MEMBER(i8251_device::txrdy_r)
{
return is_tx_enabled() && (m_status & I8251_STATUS_TX_READY) != 0;
}
void v5x_scu_device::device_start()
{
i8251_device::device_start();
save_item(NAME(m_simk));
}
void v5x_scu_device::device_reset()
{
// FIXME: blindly copied from v53.cpp - not verified
m_simk = 0x03;
i8251_device::device_reset();
}
u8 v5x_scu_device::read(offs_t offset)
{
u8 data = 0;
switch (offset)
{
case 0: data = data_r(); break;
case 1: data = status_r(); break;
case 2: break;
case 3: data = simk_r(); break;
}
return data;
}
void v5x_scu_device::write(offs_t offset, uint8_t data)
{
switch (offset)
{
case 0: data_w(data); break;
case 1: control_w(data); break;
case 2: mode_w(data); break;
case 3: simk_w(data); break;
}
}