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Diffstat (limited to 'trunk/src/emu/machine/adc0808.c')
-rw-r--r-- | trunk/src/emu/machine/adc0808.c | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/trunk/src/emu/machine/adc0808.c b/trunk/src/emu/machine/adc0808.c new file mode 100644 index 00000000000..1c7f125e026 --- /dev/null +++ b/trunk/src/emu/machine/adc0808.c @@ -0,0 +1,171 @@ +/********************************************************************** + + National Semiconductor ADC0808/ADC0809 8-Bit A/D Converter emulation + + Copyright MESS Team. + Visit http://mamedev.org for licensing and usage restrictions. + +**********************************************************************/ + +#include "emu.h" +#include "adc0808.h" +#include "machine/devhelpr.h" + + + + +//************************************************************************** +// LIVE DEVICE +//************************************************************************** + +// device type definition +const device_type ADC0808 = &device_creator<adc0808_device>; + +//------------------------------------------------- +// adc0808_device - constructor +//------------------------------------------------- + +adc0808_device::adc0808_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) + : device_t(mconfig, ADC0808, "ADC0808", tag, owner, clock), + m_address(0), + m_start(0), + m_next_eoc(0), + m_cycle(0) +{ +} + + +//------------------------------------------------- +// device_config_complete - perform any +// operations now that the configuration is +// complete +//------------------------------------------------- + +void adc0808_device::device_config_complete() +{ + // inherit a copy of the static data + const adc0808_interface *intf = reinterpret_cast<const adc0808_interface *>(static_config()); + if (intf != NULL) + *static_cast<adc0808_interface *>(this) = *intf; + + // or initialize to defaults if none provided + else + { + memset(&m_out_eoc_cb, 0, sizeof(m_out_eoc_cb)); + } +} + + +//------------------------------------------------- +// device_start - device-specific startup +//------------------------------------------------- + +void adc0808_device::device_start() +{ + // resolve callbacks + m_out_eoc_func.resolve(m_out_eoc_cb, *this); + + // allocate timers + m_cycle_timer = timer_alloc(); + m_cycle_timer->adjust(attotime::zero, 0, attotime::from_hz(clock())); + + // register for state saving + save_item(NAME(m_address)); + save_item(NAME(m_start)); + save_item(NAME(m_eoc)); + save_item(NAME(m_next_eoc)); + save_item(NAME(m_sar)); + save_item(NAME(m_cycle)); + save_item(NAME(m_bit)); +} + + +//------------------------------------------------- +// device_timer - handler timer events +//------------------------------------------------- + +void adc0808_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) +{ + if (!m_start) + { + if (m_cycle == 7) + { + m_bit++; + + if (m_bit == 8) + { + /* sample input */ + double vref_pos = m_in_vref_pos_func(this); + double vref_neg = m_in_vref_neg_func(this); + + double input = m_in_in_func[m_address](this); + + m_sar = (255 * (input - vref_neg)) / (vref_pos - vref_neg); + + /* trigger end of conversion */ + m_next_eoc = 1; + } + } + } + + if (m_cycle == 0) + { + /* set end of conversion pin */ + if (m_next_eoc != m_eoc) + { + m_out_eoc_func(m_next_eoc); + m_eoc = m_next_eoc; + } + } + + m_cycle++; + + if (m_cycle == 8) + { + m_cycle = 0; + } +} + + +//------------------------------------------------- +// data_r - data read +//------------------------------------------------- + +READ8_MEMBER( adc0808_device::data_r ) +{ + return m_sar; +} + + +//------------------------------------------------- +// ale_w - address write +//------------------------------------------------- + +WRITE8_MEMBER( adc0808_device::ale_w ) +{ + m_address = data; +} + + +//------------------------------------------------- +// start_w - start conversion +//------------------------------------------------- + +WRITE_LINE_MEMBER( adc0808_device::start_w ) +{ + if (!m_start && state) // rising edge + { + // reset registers + + m_sar = 0; + m_bit = 0; + } + else if (m_start && !state) // falling edge + { + // start conversion + + m_next_eoc = 0; + } + + m_start = state; +} |