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-rw-r--r--src/devices/bus/bml3/rtc.cpp109
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diff --git a/src/devices/bus/bml3/rtc.cpp b/src/devices/bus/bml3/rtc.cpp
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+// 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)));
+}