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Diffstat (limited to 'src/devices/bus/bml3/rtc.cpp')
-rw-r--r-- | src/devices/bus/bml3/rtc.cpp | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/src/devices/bus/bml3/rtc.cpp b/src/devices/bus/bml3/rtc.cpp new file mode 100644 index 00000000000..eb672aaede0 --- /dev/null +++ b/src/devices/bus/bml3/rtc.cpp @@ -0,0 +1,109 @@ +// license:GPL-2.0+ +// copyright-holders:Russell Bull +/********************************************************************* + + bml3rtc.cpp + + Hitachi RTC card for the MB-6890 + + I cannot find any reference to the original Hitachi board that + had this feature, but I was given a schematic back in the 1980's + and I designed a board that included the circuitry. + The standard ROM supported this battery-backed RTC and detects + it's presence on start up. + +*********************************************************************/ + +#include "emu.h" +#include "rtc.h" + + +//************************************************************************** +// DEVICE DEFINITIONS +//************************************************************************** + +DEFINE_DEVICE_TYPE(BML3BUS_RTC, bml3bus_rtc_device, "bml3rtc", "Hitachi Real Time Clock Card") + + +//------------------------------------------------- +// device_add_mconfig - add device configuration +//------------------------------------------------- + +void bml3bus_rtc_device::device_add_mconfig(machine_config &config) +{ + MSM5832(config, m_rtc, 32.768_kHz_XTAL); +} + + +uint8_t bml3bus_rtc_device::read(offs_t offset) +{ + uint8_t data = 0x00; + + if (offset == 2) // read @ 0xff3a + { + if (BIT(m_addr_latch, 7)) //bit 7 is the !write buffer enable + { + data = m_rtc->data_r(); + } + else + { + data = m_data_latch; //the Hitachi ROM code detects RTC presence by reading back what it wrote to the data latch + } + } + return data | 0xf0; // return low nibble only +} + +void bml3bus_rtc_device::write(offs_t offset, uint8_t data) +{ + switch (offset) + { + case 0: // addr latch @ 0xff38 + m_rtc->cs_w(1); //always selected + m_rtc->write_w(BIT(data, 6)); + m_rtc->read_w(BIT(data, 7)); + m_rtc->address_w(data & 0x0f); + + m_addr_latch = data; + break; + + case 1: // data latch @ 0xff39 + m_rtc->hold_w(BIT(data, 6)); + + if (BIT(m_addr_latch, 6)) + { + m_rtc->data_w(data & 0x0f); + } + + m_data_latch = data; + break; + } +} +//************************************************************************** +// LIVE DEVICE +//************************************************************************** + +bml3bus_rtc_device::bml3bus_rtc_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) + : device_t(mconfig, BML3BUS_RTC, tag, owner, clock) + , device_bml3bus_card_interface(mconfig, *this) + , m_rtc(*this, "rtc") +{ +} + +//------------------------------------------------- +// device_start - device-specific startup +//------------------------------------------------- + +void bml3bus_rtc_device::device_start() +{ + m_addr_latch = 0; + m_data_latch = 0; + + save_item(NAME(m_addr_latch)); + save_item(NAME(m_data_latch)); +} + +void bml3bus_rtc_device::map_io(address_space_installer &space) +{ + // install into memory + space.install_readwrite_handler(0xff38, 0xff3a, read8sm_delegate(*this, FUNC(bml3bus_rtc_device::read)), write8sm_delegate(*this, FUNC(bml3bus_rtc_device::write))); +} |