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// license:BSD-3-Clause
// copyright-holders:Curt Coder,AJR
/**********************************************************************
Intel 8155/8156 - 2048-Bit Static MOS RAM with I/O Ports and Timer
The timer primarily functions as a square-wave generator, but can
also be programmed for a single-cycle low pulse on terminal count.
The only difference between 8155 and 8156 is that pin 8 (CE) is
active low on the former device and active high on the latter.
National's NSC810 RAM-I/O-Timer is pin-compatible with the Intel
8156, but has different I/O registers (including a second timer)
with incompatible mapping.
**********************************************************************/
/*
TODO:
- ALT 3 and ALT 4 strobed port modes
- optional NVRAM backup for CMOS versions
*/
#include "emu.h"
#include "i8155.h"
// device type definitions
DEFINE_DEVICE_TYPE(I8155, i8155_device, "i8155", "Intel 8155 RAM, I/O & Timer")
DEFINE_DEVICE_TYPE(I8156, i8156_device, "i8156", "Intel 8156 RAM, I/O & Timer")
//**************************************************************************
// MACROS / CONSTANTS
//**************************************************************************
#define LOG_PORT (1U << 1)
#define LOG_TIMER (1U << 2)
#define VERBOSE (0)
#include "logmacro.h"
enum
{
REGISTER_COMMAND = 0,
REGISTER_STATUS = 0,
REGISTER_PORT_A,
REGISTER_PORT_B,
REGISTER_PORT_C,
REGISTER_TIMER_LOW,
REGISTER_TIMER_HIGH
};
enum
{
PORT_A = 0,
PORT_B,
PORT_C,
PORT_COUNT
};
enum
{
PORT_MODE_INPUT = 0,
PORT_MODE_OUTPUT,
PORT_MODE_STROBED_PORT_A, // not supported
PORT_MODE_STROBED // not supported
};
enum
{
MEMORY = 0,
IO
};
#define COMMAND_PA 0x01
#define COMMAND_PB 0x02
#define COMMAND_PC_MASK 0x0c
#define COMMAND_PC_ALT_1 0x00
#define COMMAND_PC_ALT_2 0x0c
#define COMMAND_PC_ALT_3 0x04 // not supported
#define COMMAND_PC_ALT_4 0x08 // not supported
#define COMMAND_IEA 0x10 // not supported
#define COMMAND_IEB 0x20 // not supported
#define COMMAND_TM_MASK 0xc0
#define COMMAND_TM_NOP 0x00
#define COMMAND_TM_STOP 0x40
#define COMMAND_TM_STOP_AFTER_TC 0x80
#define COMMAND_TM_START 0xc0
#define STATUS_INTR_A 0x01 // not supported
#define STATUS_A_BF 0x02 // not supported
#define STATUS_INTE_A 0x04 // not supported
#define STATUS_INTR_B 0x08 // not supported
#define STATUS_B_BF 0x10 // not supported
#define STATUS_INTE_B 0x20 // not supported
#define STATUS_TIMER 0x40
#define TIMER_MODE_MASK 0xc0
#define TIMER_MODE_AUTO_RELOAD 0x40
#define TIMER_MODE_TC_PULSE 0x80
//**************************************************************************
// INLINE HELPERS
//**************************************************************************
inline uint8_t i8155_device::get_timer_mode() const
{
return (m_count_loaded >> 8) & TIMER_MODE_MASK;
}
inline uint16_t i8155_device::get_timer_count() const
{
if (m_timer->enabled())
{
// timer counts down by twos
return std::min((uint16_t(attotime_to_clocks(m_timer->remaining())) + 1) << 1, m_count_loaded & 0x3ffe) | (m_count_even_phase ? 0 : 1);
}
else
return m_count_length;
}
inline void i8155_device::timer_output(int to)
{
if (to == m_to)
return;
m_to = to;
m_out_to_cb(to);
LOGMASKED(LOG_TIMER, "Timer output: %u\n", to);
}
inline void i8155_device::timer_stop_count()
{
// stop counting
if (m_timer->enabled())
{
m_count_loaded = (m_count_loaded & (TIMER_MODE_MASK << 8)) | get_timer_count();
m_timer->enable(false);
}
m_timer_tc->enable(false);
// clear timer output
timer_output(1);
}
inline void i8155_device::timer_reload_count()
{
m_count_loaded = m_count_length;
// valid counts range from 2 to 3FFF
if ((m_count_length & 0x3fff) < 2)
{
timer_stop_count();
return;
}
// begin the odd half of the count, with one extra cycle if count is odd
m_count_even_phase = false;
// set up our timer
m_timer->adjust(clocks_to_attotime(((m_count_length & 0x3ffe) >> 1) + (m_count_length & 1)));
timer_output(1);
switch (get_timer_mode())
{
case 0:
// puts out LOW during second half of count
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: LOW)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_AUTO_RELOAD:
// square wave, i.e. the period of the square wave equals the count length programmed with automatic reload at terminal count
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Square wave)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_TC_PULSE:
// single pulse upon TC being reached
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Single pulse)\n", m_count_loaded & 0x3fff);
break;
case TIMER_MODE_TC_PULSE | TIMER_MODE_AUTO_RELOAD:
// automatic reload, i.e. single pulse every time TC is reached
LOGMASKED(LOG_TIMER, "Timer loaded with %d (Mode: Automatic reload)\n", m_count_loaded & 0x3fff);
break;
}
}
inline int i8155_device::get_port_mode(int port)
{
int mode = -1;
switch (port)
{
case PORT_A:
mode = (m_command & COMMAND_PA) ? PORT_MODE_OUTPUT : PORT_MODE_INPUT;
break;
case PORT_B:
mode = (m_command & COMMAND_PB) ? PORT_MODE_OUTPUT : PORT_MODE_INPUT;
break;
case PORT_C:
switch (m_command & COMMAND_PC_MASK)
{
case COMMAND_PC_ALT_1: mode = PORT_MODE_INPUT; break;
case COMMAND_PC_ALT_2: mode = PORT_MODE_OUTPUT; break;
case COMMAND_PC_ALT_3: mode = PORT_MODE_STROBED_PORT_A; break;
case COMMAND_PC_ALT_4: mode = PORT_MODE_STROBED; break;
}
break;
}
return mode;
}
inline uint8_t i8155_device::read_port(int port)
{
uint8_t data = 0;
switch (get_port_mode(port))
{
case PORT_MODE_INPUT:
data = (port == PORT_A) ? m_in_pa_cb(0) : ((port == PORT_B) ? m_in_pb_cb(0) : m_in_pc_cb(0));
break;
case PORT_MODE_OUTPUT:
data = m_output[port];
break;
default:
// strobed mode not implemented yet
logerror("8155 Unsupported Port C mode!\n");
break;
}
return data;
}
inline void i8155_device::write_port(int port, uint8_t data)
{
m_output[port] = data;
switch (get_port_mode(port))
{
case PORT_MODE_OUTPUT:
if (port == PORT_A)
m_out_pa_cb((offs_t)0, m_output[port]);
else if (port == PORT_B)
m_out_pb_cb((offs_t)0, m_output[port]);
else
m_out_pc_cb((offs_t)0, m_output[port]);
break;
}
}
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// i8155_device - constructor
//-------------------------------------------------
i8155_device::i8155_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
i8155_device(mconfig, I8155, tag, owner, clock)
{
}
i8155_device::i8155_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock) :
device_t(mconfig, type, tag, owner, clock),
m_in_pa_cb(*this, 0),
m_in_pb_cb(*this, 0),
m_in_pc_cb(*this, 0),
m_out_pa_cb(*this),
m_out_pb_cb(*this),
m_out_pc_cb(*this),
m_out_to_cb(*this),
m_command(0),
m_status(0),
m_count_length(0),
m_count_loaded(0),
m_to(0),
m_count_even_phase(false)
{
}
//-------------------------------------------------
// i8156_device - constructor
//-------------------------------------------------
i8156_device::i8156_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
i8155_device(mconfig, I8156, tag, owner, clock)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void i8155_device::device_start()
{
// allocate RAM
m_ram = make_unique_clear<uint8_t[]>(256);
// allocate timers
m_timer = timer_alloc(FUNC(i8155_device::timer_half_counted), this);
m_timer_tc = timer_alloc(FUNC(i8155_device::timer_tc), this);
// register for state saving
save_item(NAME(m_io_m));
save_item(NAME(m_ad));
save_item(NAME(m_command));
save_item(NAME(m_status));
save_item(NAME(m_output));
save_pointer(NAME(m_ram), 256);
save_item(NAME(m_count_length));
save_item(NAME(m_count_loaded));
save_item(NAME(m_to));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void i8155_device::device_reset()
{
// clear output registers
m_output[PORT_A] = 0;
m_output[PORT_B] = 0;
m_output[PORT_C] = 0;
// set ports to input mode
register_w(REGISTER_COMMAND, m_command & ~(COMMAND_PA | COMMAND_PB | COMMAND_PC_MASK));
// clear timer flag
m_status &= ~STATUS_TIMER;
// stop timer
timer_stop_count();
}
//-------------------------------------------------
// timer_half_counted - handler timer events
//-------------------------------------------------
TIMER_CALLBACK_MEMBER(i8155_device::timer_half_counted)
{
if (m_count_even_phase)
{
timer_output(1);
m_count_even_phase = false;
if ((get_timer_mode() & TIMER_MODE_AUTO_RELOAD) == 0 || (m_command & COMMAND_TM_MASK) == COMMAND_TM_STOP_AFTER_TC)
{
// stop timer
timer_stop_count();
LOGMASKED(LOG_TIMER, "Timer stopped\n");
}
else
{
// automatically reload the counter
timer_reload_count();
}
}
else
{
LOGMASKED(LOG_TIMER, "Timer count half finished\n");
// reload the even half of the count
m_timer->adjust(clocks_to_attotime((m_count_loaded & 0x3ffe) >> 1));
m_count_even_phase = true;
// square wave modes produce a low output in the second half of the counting period
if ((get_timer_mode() & TIMER_MODE_TC_PULSE) == 0)
timer_output(0);
else
m_timer_tc->adjust(clocks_to_attotime((std::max(m_count_loaded & 0x3ffe, 2) - 2) >> 1));
}
}
//-------------------------------------------------
// timer_tc - generate TC low pulse
//-------------------------------------------------
TIMER_CALLBACK_MEMBER(i8155_device::timer_tc)
{
if ((get_timer_mode() & TIMER_MODE_TC_PULSE) != 0)
{
// pulse low on TC being reached
timer_output(0);
}
// set timer flag
m_status |= STATUS_TIMER;
}
//-------------------------------------------------
// io_r - register read
//-------------------------------------------------
uint8_t i8155_device::io_r(offs_t offset)
{
uint8_t data = 0;
switch (offset & 0x07)
{
case REGISTER_STATUS:
data = m_status;
// clear timer flag
if (!machine().side_effects_disabled())
m_status &= ~STATUS_TIMER;
break;
case REGISTER_PORT_A:
data = read_port(PORT_A);
break;
case REGISTER_PORT_B:
data = read_port(PORT_B);
break;
case REGISTER_PORT_C:
data = read_port(PORT_C) | 0xc0;
break;
case REGISTER_TIMER_LOW:
data = get_timer_count() & 0xff;
break;
case REGISTER_TIMER_HIGH:
data = (get_timer_count() >> 8 & 0x3f) | get_timer_mode();
break;
}
return data;
}
//-------------------------------------------------
// write_command - set port modes and start/stop
// timer
//-------------------------------------------------
void i8155_device::write_command(uint8_t data)
{
uint8_t old_command = std::exchange(m_command, data);
LOGMASKED(LOG_PORT, "Port A Mode: %s\n", (data & COMMAND_PA) ? "output" : "input");
LOGMASKED(LOG_PORT, "Port B Mode: %s\n", (data & COMMAND_PB) ? "output" : "input");
LOGMASKED(LOG_PORT, "Port A Interrupt: %s\n", (data & COMMAND_IEA) ? "enabled" : "disabled");
LOGMASKED(LOG_PORT, "Port B Interrupt: %s\n", (data & COMMAND_IEB) ? "enabled" : "disabled");
if ((data & COMMAND_PA) && (~old_command & COMMAND_PA))
m_out_pa_cb((offs_t)0, m_output[PORT_A]);
if ((data & COMMAND_PB) && (~old_command & COMMAND_PB))
m_out_pb_cb((offs_t)0, m_output[PORT_B]);
switch (data & COMMAND_PC_MASK)
{
case COMMAND_PC_ALT_1:
LOGMASKED(LOG_PORT, "Port C Mode: Alt 1 (PC0-PC5 input)\n");
break;
case COMMAND_PC_ALT_2:
LOGMASKED(LOG_PORT, "Port C Mode: Alt 2 (PC0-PC5 output)\n");
if ((old_command & COMMAND_PC_MASK) != COMMAND_PC_ALT_2)
m_out_pc_cb((offs_t)0, m_output[PORT_C]);
break;
case COMMAND_PC_ALT_3:
LOGMASKED(LOG_PORT, "Port C Mode: Alt 3 (PC0-PC2 A handshake, PC3-PC5 output)\n");
break;
case COMMAND_PC_ALT_4:
LOGMASKED(LOG_PORT, "Port C Mode: Alt 4 (PC0-PC2 A handshake, PC3-PC5 B handshake)\n");
break;
}
switch (data & COMMAND_TM_MASK)
{
case COMMAND_TM_NOP:
// do not affect counter operation
break;
case COMMAND_TM_STOP:
// NOP if timer has not started, stop counting if the timer is running
LOGMASKED(LOG_PORT, "Timer Command: Stop\n");
timer_stop_count();
break;
case COMMAND_TM_STOP_AFTER_TC:
// stop immediately after present TC is reached (NOP if timer has not started)
LOGMASKED(LOG_PORT, "Timer Command: Stop after TC\n");
break;
case COMMAND_TM_START:
LOGMASKED(LOG_PORT, "Timer Command: Start\n");
if (m_timer->enabled())
{
// if timer is running, start the new mode and CNT length immediately after present TC is reached
}
else
{
// load mode and CNT length and start immediately after loading (if timer is not running)
timer_reload_count();
}
break;
}
}
//-------------------------------------------------
// register_w - register write
//-------------------------------------------------
void i8155_device::register_w(int offset, uint8_t data)
{
switch (offset & 0x07)
{
case REGISTER_COMMAND:
write_command(data);
break;
case REGISTER_PORT_A:
write_port(PORT_A, data);
break;
case REGISTER_PORT_B:
write_port(PORT_B, data);
break;
case REGISTER_PORT_C:
write_port(PORT_C, data & 0x3f);
break;
case REGISTER_TIMER_LOW:
m_count_length = (m_count_length & 0xff00) | data;
break;
case REGISTER_TIMER_HIGH:
m_count_length = (data << 8) | (m_count_length & 0xff);
break;
}
}
//-------------------------------------------------
// io_w - register write
//-------------------------------------------------
void i8155_device::io_w(offs_t offset, uint8_t data)
{
register_w(offset, data);
}
//-------------------------------------------------
// memory_r - internal RAM read
//-------------------------------------------------
uint8_t i8155_device::memory_r(offs_t offset)
{
return m_ram[offset & 0xff];
}
//-------------------------------------------------
// memory_w - internal RAM write
//-------------------------------------------------
void i8155_device::memory_w(offs_t offset, uint8_t data)
{
m_ram[offset & 0xff] = data;
}
//-------------------------------------------------
// ale_w - address latch write
//-------------------------------------------------
void i8155_device::ale_w(offs_t offset, uint8_t data)
{
// I/O / memory select
m_io_m = BIT(offset, 0);
// address
m_ad = data;
}
//-------------------------------------------------
// data_r - memory or I/O read
//-------------------------------------------------
uint8_t i8155_device::data_r()
{
uint8_t data = 0;
switch (m_io_m)
{
case MEMORY:
data = memory_r(m_ad);
break;
case IO:
data = io_r(m_ad);
break;
}
return data;
}
//-------------------------------------------------
// data_w - memory or I/O write
//-------------------------------------------------
void i8155_device::data_w(uint8_t data)
{
switch (m_io_m)
{
case MEMORY:
memory_w(m_ad, data);
break;
case IO:
io_w(m_ad, data);
break;
}
}
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