diff options
Diffstat (limited to 'src/devices/machine/i8155.cpp')
| -rw-r--r-- | src/devices/machine/i8155.cpp | 243 |
1 files changed, 138 insertions, 105 deletions
diff --git a/src/devices/machine/i8155.cpp b/src/devices/machine/i8155.cpp index f543ec4573f..9fb4251bb11 100644 --- a/src/devices/machine/i8155.cpp +++ b/src/devices/machine/i8155.cpp @@ -1,8 +1,11 @@ // license:BSD-3-Clause -// copyright-holders:Curt Coder +// copyright-holders:Curt Coder,AJR /********************************************************************** - Intel 8155/8156 - 2048-Bit Static MOS RAM with I/O Ports and Timer emulation + 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. @@ -17,7 +20,8 @@ TODO: - - strobed mode + - ALT 3 and ALT 4 strobed port modes + - optional NVRAM backup for CMOS versions */ @@ -26,15 +30,18 @@ // device type definitions -DEFINE_DEVICE_TYPE(I8155, i8155_device, "i8155", "Intel 8155 RIOT") -const device_type I8156 = I8155; +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 0 +#define LOG_PORT (1U << 0) +#define LOG_TIMER (1U << 1) +#define VERBOSE (LOG_PORT | LOG_TIMER) +#include "logmacro.h" enum { @@ -93,10 +100,8 @@ enum #define STATUS_TIMER 0x40 #define TIMER_MODE_MASK 0xc0 -#define TIMER_MODE_LOW 0x00 -#define TIMER_MODE_SQUARE_WAVE 0x40 -#define TIMER_MODE_SINGLE_PULSE 0x80 -#define TIMER_MODE_AUTOMATIC_RELOAD 0xc0 +#define TIMER_MODE_AUTO_RELOAD 0x40 +#define TIMER_MODE_TC_PULSE 0x80 @@ -117,20 +122,70 @@ ADDRESS_MAP_END inline uint8_t i8155_device::get_timer_mode() { - return (m_count_length >> 8) & TIMER_MODE_MASK; + return (m_count_loaded >> 8) & TIMER_MODE_MASK; +} + +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_output() +inline void i8155_device::timer_stop_count() { - m_out_to_cb(m_to); + // stop counting + m_timer->enable(0); - if (LOG) logerror("8155 Timer Output: %u\n", m_to); + // clear timer output + timer_output(1); } -inline void i8155_device::pulse_timer_output() +inline void i8155_device::timer_reload_count() { - m_to = 0; timer_output(); - m_to = 1; timer_output(); + // valid counts range from 2 to 3FFF + if ((m_count_length & 0x3fff) < 2) + { + timer_stop_count(); + return; + } + + m_count_loaded = m_count_length; + + // begin the odd half of the count, with one extra cycle if count is odd + m_counter = (m_count_loaded & 0x3ffe) | 1; + m_count_extra = BIT(m_count_loaded, 0); + + // set up our timer + m_timer->adjust(attotime::zero, 0, clocks_to_attotime(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) @@ -210,7 +265,12 @@ inline void i8155_device::write_port(int port, uint8_t data) //------------------------------------------------- i8155_device::i8155_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) - : device_t(mconfig, I8155, tag, owner, 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), device_memory_interface(mconfig, *this), m_in_pa_cb(*this), m_in_pb_cb(*this), @@ -221,12 +281,27 @@ i8155_device::i8155_device(const machine_config &mconfig, const char *tag, devic m_out_to_cb(*this), m_command(0), m_status(0), + m_count_length(0), + m_count_loaded(0), + m_counter(0), + m_count_extra(false), + m_to(0), m_space_config("ram", ENDIANNESS_LITTLE, 8, 8, 0, nullptr, *ADDRESS_MAP_NAME(i8155)) { } //------------------------------------------------- +// 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 //------------------------------------------------- @@ -251,6 +326,8 @@ void i8155_device::device_start() save_item(NAME(m_status)); save_item(NAME(m_output)); save_item(NAME(m_count_length)); + save_item(NAME(m_count_loaded)); + save_item(NAME(m_count_extra)); save_item(NAME(m_counter)); save_item(NAME(m_to)); } @@ -273,12 +350,8 @@ void i8155_device::device_reset() // clear timer flag m_status &= ~STATUS_TIMER; - // stop counting - m_timer->enable(0); - - // clear timer output - m_to = 1; - timer_output(); + // stop timer + timer_stop_count(); } @@ -288,60 +361,52 @@ void i8155_device::device_reset() void i8155_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) { - // count down - m_counter--; - - if (get_timer_mode() == TIMER_MODE_LOW) + if (m_count_extra) { - // pulse on every count - pulse_timer_output(); + m_count_extra = false; + return; } - if (m_counter == 0) + // count down by twos + m_counter -= 2; + + if (m_counter == 1) { - if (LOG) logerror("8155 Timer Count Reached\n"); + LOGMASKED(LOG_TIMER, "Timer count half finished\n"); - switch (get_timer_mode()) - { - case TIMER_MODE_LOW: - case TIMER_MODE_SQUARE_WAVE: - // toggle timer output - m_to = !m_to; - timer_output(); - break; + // reload the even half of the count + m_counter = m_count_loaded & 0x3ffe; - case TIMER_MODE_SINGLE_PULSE: - case TIMER_MODE_AUTOMATIC_RELOAD: - // pulse upon TC being reached - pulse_timer_output(); - break; + // 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 if (m_counter == 2) + { + 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; + } + else if (m_counter == 0) + { + timer_output(1); - if ((m_command & COMMAND_TM_MASK) == COMMAND_TM_START) - { - // load new timer counter - m_counter = m_count_length & 0x3fff; - - if (LOG) logerror("8155 Timer New Start\n"); - } - else if ((m_command & COMMAND_TM_MASK) == COMMAND_TM_STOP_AFTER_TC || get_timer_mode() == TIMER_MODE_SINGLE_PULSE) + if ((get_timer_mode() & TIMER_MODE_AUTO_RELOAD) == 0 || (m_command & COMMAND_TM_MASK) == COMMAND_TM_STOP_AFTER_TC) { // stop timer - m_timer->enable(0); - - if (LOG) logerror("8155 Timer Stopped\n"); + timer_stop_count(); + LOGMASKED(LOG_TIMER, "Timer stopped\n"); } else { // automatically reload the counter - m_counter = m_count_length & 0x3fff; + timer_reload_count(); } - - // clear timer command - m_command &= ~COMMAND_TM_MASK; } } @@ -412,28 +477,28 @@ void i8155_device::register_w(int offset, uint8_t data) case REGISTER_COMMAND: m_command = data; - if (LOG) logerror("8155 Port A Mode: %s\n", (data & COMMAND_PA) ? "output" : "input"); - if (LOG) logerror("8155 Port B Mode: %s\n", (data & COMMAND_PB) ? "output" : "input"); + 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"); - if (LOG) logerror("8155 Port A Interrupt: %s\n", (data & COMMAND_IEA) ? "enabled" : "disabled"); - if (LOG) logerror("8155 Port B Interrupt: %s\n", (data & COMMAND_IEB) ? "enabled" : "disabled"); + 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"); switch (data & COMMAND_PC_MASK) { case COMMAND_PC_ALT_1: - if (LOG) logerror("8155 Port C Mode: Alt 1\n"); + LOGMASKED(LOG_PORT, "Port C Mode: Alt 1\n"); break; case COMMAND_PC_ALT_2: - if (LOG) logerror("8155 Port C Mode: Alt 2\n"); + LOGMASKED(LOG_PORT, "Port C Mode: Alt 2\n"); break; case COMMAND_PC_ALT_3: - if (LOG) logerror("8155 Port C Mode: Alt 3\n"); + LOGMASKED(LOG_PORT, "Port C Mode: Alt 3\n"); break; case COMMAND_PC_ALT_4: - if (LOG) logerror("8155 Port C Mode: Alt 4\n"); + LOGMASKED(LOG_PORT, "Port C Mode: Alt 4\n"); break; } @@ -445,19 +510,17 @@ void i8155_device::register_w(int offset, uint8_t data) case COMMAND_TM_STOP: // NOP if timer has not started, stop counting if the timer is running - if (LOG) logerror("8155 Timer Command: Stop\n"); - m_to = 1; - timer_output(); - m_timer->enable(0); + 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) - if (LOG) logerror("8155 Timer Command: Stop after TC\n"); + LOGMASKED(LOG_PORT, "Timer Command: Stop after TC\n"); break; case COMMAND_TM_START: - if (LOG) logerror("8155 Timer Command: Start\n"); + LOGMASKED(LOG_PORT, "Timer Command: Start\n"); if (m_timer->enabled()) { @@ -466,12 +529,7 @@ void i8155_device::register_w(int offset, uint8_t data) else { // load mode and CNT length and start immediately after loading (if timer is not running) - m_counter = m_count_length & 0x3fff; - if (clock() > 0) // a clock of 0 causes MAME to freeze. - m_timer->adjust(attotime::zero, 0, attotime::from_hz(clock())); - - // clear timer command so this won't execute twice - m_command &= ~COMMAND_TM_MASK; + timer_reload_count(); } break; } @@ -491,35 +549,10 @@ void i8155_device::register_w(int offset, uint8_t data) case REGISTER_TIMER_LOW: m_count_length = (m_count_length & 0xff00) | data; - if (LOG) logerror("8155 Count Length Low: %04x\n", m_count_length); break; case REGISTER_TIMER_HIGH: m_count_length = (data << 8) | (m_count_length & 0xff); - if (LOG) logerror("8155 Count Length High: %04x\n", m_count_length); - - switch (data & TIMER_MODE_MASK) - { - case TIMER_MODE_LOW: - // puts out LOW during second half of count - if (LOG) logerror("8155 Timer Mode: LOW\n"); - break; - - case TIMER_MODE_SQUARE_WAVE: - // square wave, i.e. the period of the square wave equals the count length programmed with automatic reload at terminal count - if (LOG) logerror("8155 Timer Mode: Square wave\n"); - break; - - case TIMER_MODE_SINGLE_PULSE: - // single pulse upon TC being reached - if (LOG) logerror("8155 Timer Mode: Single pulse\n"); - break; - - case TIMER_MODE_AUTOMATIC_RELOAD: - // automatic reload, i.e. single pulse every time TC is reached - if (LOG) logerror("8155 Timer Mode: Automatic reload\n"); - break; - } break; } } |