diff --git a/scripts/src/machine.lua b/scripts/src/machine.lua
index e9a8fda147e..04104393f9f 100644
--- a/scripts/src/machine.lua
+++ b/scripts/src/machine.lua
@@ -3565,6 +3565,18 @@ if (MACHINES["MM58167"]~=null) then
 	}
 end
 
+---------------------------------------------------
+--
+--@src/devices/machine/mm58174.h,MACHINES["MM58174"] = true
+---------------------------------------------------
+
+if (MACHINES["MM58174"]~=null) then
+	files {
+		MAME_DIR .. "src/devices/machine/mm58174.cpp",
+		MAME_DIR .. "src/devices/machine/mm58174.h",
+	}
+end
+
 
 ---------------------------------------------------
 --
diff --git a/src/devices/machine/mm58174.cpp b/src/devices/machine/mm58174.cpp
new file mode 100644
index 00000000000..fe24c8091b5
--- /dev/null
+++ b/src/devices/machine/mm58174.cpp
@@ -0,0 +1,304 @@
+// license:BSD-3-Clause
+// copyright-holders:Raphael Nabet,Sergey Svishchev
+/***************************************************************************
+
+    mm58174.cpp
+
+    National Semiconductor MM58174 Microprocessor Compatible Real Time Clock
+
+    Docs:
+    * <http://www.bitsavers.org/components/national/_appNotes/AN-0359.pdf>
+    * <ftp://ftp.jameco.com/Archive/Obsolete-TechDocuments/26219.pdf>
+
+    Todo:
+    * data-changed flip-flop
+    * interrupts, MM58174A (no interrupt ack)
+    * loss of accuracy after restart
+
+***************************************************************************/
+
+#include "emu.h"
+#include "machine/mm58174.h"
+
+enum
+{
+	ctl_clkrun = 0x1,  /* clock start/stop (1=run, 0=stop) */
+
+	year_leap = 0x8,
+
+	int_ctl_rpt = 0x8,  /* 1 for repeated interrupt */
+	int_ctl_dly = 0x7   /* 0 no interrupt, 1 = .5 second, 2=5, 4=60 */
+};
+
+
+DEFINE_DEVICE_TYPE(MM58174, mm58174_device, "mm58174", "National Semiconductor MM58174 RTC")
+
+
+mm58174_device::mm58174_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
+	: device_t(mconfig, MM58174, tag, owner, clock),
+		device_rtc_interface(mconfig, *this)
+{
+}
+
+
+//-------------------------------------------------
+//  device_start - device-specific startup
+//-------------------------------------------------
+
+void mm58174_device::device_start()
+{
+	m_increment_rtc = timer_alloc();
+	m_increment_rtc->adjust(attotime::zero, 0, attotime::from_msec(100));
+	m_interrupt_timer = timer_alloc();
+
+	// register for state saving
+	save_item(NAME(m_control));
+	save_item(NAME(m_int_ctl));
+	save_item(NAME(m_wday));
+	save_item(NAME(m_months1));
+	save_item(NAME(m_months2));
+	save_item(NAME(m_days1));
+	save_item(NAME(m_days2));
+	save_item(NAME(m_hours1));
+	save_item(NAME(m_hours2));
+	save_item(NAME(m_minutes1));
+	save_item(NAME(m_minutes2));
+	save_item(NAME(m_seconds1));
+	save_item(NAME(m_seconds2));
+	save_item(NAME(m_tenths));
+}
+
+//-------------------------------------------------
+//  device_reset - device-specific reset
+//-------------------------------------------------
+
+void mm58174_device::device_reset()
+{
+	m_tenths = 0;
+	m_control = 0;
+}
+
+//-------------------------------------------------
+//  rtc_clock_updated -
+//-------------------------------------------------
+
+void mm58174_device::rtc_clock_updated(int year, int month, int day, int day_of_week, int hour, int minute, int second)
+{
+	m_seconds1 = second / 10;
+	m_seconds2 = second % 10;
+	m_minutes1 = minute / 10;
+	m_minutes2 = minute % 10;
+	m_hours1 = hour / 10;
+	m_hours2 = hour % 10;
+	m_wday = day_of_week;
+	m_days1 = day / 10;
+	m_days2 = day % 10;
+	m_months1 = month / 10;
+	m_months2 = month % 10;
+	m_years = 1 << (3 - (year & 3));
+}
+
+
+attotime mm58174_device::interrupt_period_table(int val)
+{
+	switch(val)
+	{
+		case 0: return attotime::from_msec(0);
+		case 1: return attotime::from_msec(500);
+		case 2: return attotime::from_seconds(5);
+		case 4: return attotime::from_seconds(60);
+		default: fatalerror("out of range\n");
+	}
+}
+
+void mm58174_device::update_rtc()
+{
+	set_clock_register(RTC_SECOND, m_seconds1 * 10 + m_seconds2);
+	set_clock_register(RTC_MINUTE, m_minutes1 * 10 + m_minutes2);
+	set_clock_register(RTC_HOUR, m_hours1 * 10 + m_hours2);
+	set_clock_register(RTC_DAY, m_days1 * 10 + m_days2);
+	set_clock_register(RTC_DAY_OF_WEEK, m_wday);
+	set_clock_register(RTC_MONTH, m_months1 * 10 + m_months2);
+}
+
+uint8_t mm58174_device::read(offs_t offset)
+{
+	int reply = 0;
+
+	offset &= 0xf;
+
+	switch (offset)
+	{
+		case 0x01:   /* Tenths of Seconds */
+			reply = m_tenths;
+			break;
+
+		case 0x02:   /* Units Seconds */
+			reply = m_seconds2;
+			break;
+
+		case 0x03:   /* Tens Seconds */
+			reply = m_seconds1;
+			break;
+
+		case 0x04:  /* Units Minutes */
+			reply = m_minutes2;
+			break;
+
+		case 0x05:   /* Tens Minutes */
+			reply = m_minutes1;
+			break;
+
+		case 0x06:   /* Units Hours */
+			reply = m_hours2;
+			break;
+
+		case 0x07:   /* Tens Hours */
+			reply = m_hours1;
+			break;
+
+		case 0x08:   /* Units Days */
+			reply = m_days2;
+			break;
+
+		case 0x09:   /* Tens Days */
+			reply = m_days1;
+			break;
+
+		case 0x0a:   /* Day of Week */
+			reply = m_wday;
+			break;
+
+		case 0x0b:   /* Units Months */
+			reply = m_months2;
+			break;
+
+		case 0x0c:   /* Tens Months */
+			reply = m_months1;
+			break;
+
+		case 0x0f:   /* Clock Setting & Interrupt Registers */
+			reply = m_int_ctl;
+			break;
+
+		default:
+			reply = 0;
+			break;
+	}
+
+	logerror("reg %02x == %02x\n", offset, reply);
+
+	return reply;
+}
+
+
+void mm58174_device::write(offs_t offset, uint8_t data)
+{
+	offset &= 0xf;
+	data &= 0xf;
+
+	logerror("reg %02x <- %02x\n", offset, data);
+
+	switch (offset)
+	{
+		case 0x00:   /* Test Mode Register (emulated) */
+			break;
+
+		case 0x01:   /* Tenths of Seconds: cannot be written */
+			break;
+
+		case 0x02:   /* Units Seconds: cannot be written */
+			break;
+
+		case 0x03:   /* Tens Seconds: cannot be written */
+			break;
+
+		case 0x04:   /* Units Minutes */
+			m_minutes2 = data;
+			update_rtc();
+			break;
+
+		case 0x05:   /* Tens Minutes */
+			m_minutes1 = data;
+			update_rtc();
+			break;
+
+		case 0x06:   /* Units Hours */
+			m_hours2 = data;
+			update_rtc();
+			break;
+
+		case 0x07:   /* Tens Hours */
+			m_hours1 = data;
+			update_rtc();
+			break;
+
+		case 0x08:   /* Units Days */
+			m_days2 = data;
+			update_rtc();
+			break;
+
+		case 0x09:   /* Tens Days */
+			m_days1 = data;
+			update_rtc();
+			break;
+
+		case 0x0a:   /* Day of Week */
+			m_wday = data;
+			update_rtc();
+			break;
+
+		case 0x0b:   /* Units Months */
+			m_months2 = data;
+			update_rtc();
+			break;
+
+		case 0x0c:   /* Tens Months */
+			m_months1 = data;
+			update_rtc();
+			break;
+
+		case 0x0d:   /* Years Status */
+			break;
+
+		case 0x0e:   /* Stop/Start */
+			if ((m_control & ctl_clkrun) && (!(data & ctl_clkrun)))  /* interrupt stop */
+				m_interrupt_timer->enable(0);
+			else if ((!(m_control & ctl_clkrun)) && (data & ctl_clkrun))   /* interrupt run */
+			{
+				attotime period = interrupt_period_table(m_int_ctl & int_ctl_dly);
+
+				m_interrupt_timer->adjust(period, 0, m_int_ctl & int_ctl_rpt ? period : attotime::zero);
+			}
+			if (!(data & ctl_clkrun)) /* stopping the clock clears the tenth counter */
+				m_tenths = 0;
+			m_control = data;
+			break;
+
+		case 0x0f:   /* Interrupt Register */
+			m_int_ctl = data;
+			if (m_control & ctl_clkrun) /* interrupt run */
+			{
+				attotime period = interrupt_period_table(m_int_ctl & int_ctl_dly);
+
+				m_interrupt_timer->adjust(period, 0, m_int_ctl & int_ctl_rpt ? period : attotime::zero);
+			}
+			break;
+	}
+}
+
+
+// Increment RTC clock (timed interrupt every 1/10s)
+void mm58174_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
+{
+	if (id > 0) return;
+
+	if (m_control & ctl_clkrun)
+	{
+		if ((++m_tenths) == 10)
+		{
+			m_tenths = 0;
+			advance_seconds();
+		}
+	}
+}
diff --git a/src/devices/machine/mm58174.h b/src/devices/machine/mm58174.h
new file mode 100644
index 00000000000..5d755627084
--- /dev/null
+++ b/src/devices/machine/mm58174.h
@@ -0,0 +1,64 @@
+// license:BSD-3-Clause
+// copyright-holders:Raphael Nabet,Sergey Svishchev
+
+#ifndef MAME_MACHINE_MM58174_H
+#define MAME_MACHINE_MM58174_H
+
+#pragma once
+
+#include "dirtc.h"
+
+/***************************************************************************
+    MACROS
+***************************************************************************/
+
+class mm58174_device : public device_t, public device_rtc_interface
+{
+public:
+	mm58174_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+	uint8_t read(offs_t offset);
+	void write(offs_t offset, uint8_t data);
+
+protected:
+	// device-level overrides
+	virtual void device_start() override;
+	virtual void device_reset() override;
+	virtual void device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) override;
+
+	// device_rtc_interface overrides
+	virtual void rtc_clock_updated(int year, int month, int day, int day_of_week, int hour, int minute, int second) override;
+	virtual bool rtc_feature_leap_year() const override { return true; }
+
+	void update_rtc();
+
+private:
+	// internal state
+
+	attotime interrupt_period_table(int val);
+
+	int m_control;    /* control register (write to address 14) */
+
+	int m_int_ctl;    /* interrupt control register */
+
+	int m_years;
+	int m_wday;       /* day of the week (1-7 (1=day1 as set in init)) */
+	int m_months1;    /* months (BCD: 1-12) */
+	int m_months2;
+	int m_days1;      /* days (BCD: 1-31) */
+	int m_days2;
+	int m_hours1;     /* hours (BCD : 0-23) */
+	int m_hours2;
+	int m_minutes1;   /* minutes (BCD : 0-59) */
+	int m_minutes2;
+	int m_seconds1;   /* seconds (BCD : 0-59) */
+	int m_seconds2;
+	int m_tenths;     /* tenths of second (BCD : 0-9) */
+
+	emu_timer *m_increment_rtc;
+	emu_timer *m_interrupt_timer;
+};
+
+DECLARE_DEVICE_TYPE(MM58174, mm58174_device)
+
+#endif // MAME_MACHINE_MM58174_H
diff --git a/src/mame/drivers/compis.cpp b/src/mame/drivers/compis.cpp
index 8037aba087d..10c7ac225c7 100644
--- a/src/mame/drivers/compis.cpp
+++ b/src/mame/drivers/compis.cpp
@@ -58,7 +58,7 @@
 #include "machine/i8251.h"
 #include "machine/i8255.h"
 #include "machine/i80130.h"
-#include "machine/mm58274c.h"
+#include "machine/mm58174.h"
 #include "machine/pic8259.h"
 #include "machine/pit8253.h"
 #include "machine/ram.h"
@@ -109,7 +109,7 @@ public:
 	required_device<i8274_device> m_mpsc;
 	required_device<centronics_device> m_centronics;
 	required_device<i8251_device> m_uart;
-	required_device<mm58274c_device> m_rtc;
+	required_device<mm58174_device> m_rtc;
 	required_device<cassette_image_device> m_cassette;
 	required_device<compis_graphics_slot_device> m_graphics;
 	required_device<isbx_slot_device> m_isbx0;
@@ -409,7 +409,7 @@ void compis_state::compis_io(address_map &map)
 	map.unmap_value_high();
 	map(0x0000, 0x0007) /* PCS0 */ .mirror(0x78).rw(m_ppi, FUNC(i8255_device::read), FUNC(i8255_device::write)).umask16(0xff00);
 	map(0x0080, 0x0087) /* PCS1 */ .mirror(0x78).rw(m_pit, FUNC(pit8253_device::read), FUNC(pit8253_device::write)).umask16(0x00ff);
-	map(0x0100, 0x011f) /* PCS2 */ .mirror(0x60).rw(m_rtc, FUNC(mm58274c_device::read), FUNC(mm58274c_device::write)).umask16(0x00ff);
+	map(0x0100, 0x011f) /* PCS2 */ .mirror(0x60).rw(m_rtc, FUNC(mm58174_device::read), FUNC(mm58174_device::write)).umask16(0x00ff);
 	map(0x0180, 0x01ff) /* PCS3 */ .rw(m_graphics, FUNC(compis_graphics_slot_device::pcs3_r), FUNC(compis_graphics_slot_device::pcs3_w));
 	//map(0x0200, 0x0201) /* PCS4 */ .mirror(0x7e);
 	map(0x0280, 0x028f) /* PCS5 */ .mirror(0x70).m(m_osp, FUNC(i80130_device::io_map));
@@ -783,9 +783,7 @@ void compis_state::compis(machine_config &config)
 	m_mpsc->out_rtsb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_rts));
 	m_mpsc->out_int_callback().set(m_maincpu, FUNC(i80186_cpu_device::int3_w));
 
-	MM58274C(config, m_rtc, 32.768_kHz_XTAL);
-	m_rtc->set_mode24(1); // 24 hour
-	m_rtc->set_day1(1);   // monday
+	MM58174(config, m_rtc, 32.768_kHz_XTAL);
 
 	CASSETTE(config, m_cassette);
 	m_cassette->set_default_state(CASSETTE_STOPPED | CASSETTE_MOTOR_DISABLED | CASSETTE_SPEAKER_ENABLED);
diff --git a/src/mame/drivers/concept.cpp b/src/mame/drivers/concept.cpp
index be1c48b03b1..32fffc75a68 100644
--- a/src/mame/drivers/concept.cpp
+++ b/src/mame/drivers/concept.cpp
@@ -231,9 +231,7 @@ void concept_state::concept(machine_config &config)
 	SPEAKER_SOUND(config, m_speaker).add_route(ALL_OUTPUTS, "mono", 1.00);
 
 	/* rtc */
-	MM58274C(config, m_mm58274, 32.768_kHz_XTAL);
-	m_mm58274->set_mode24(0); // 12 hour
-	m_mm58274->set_day1(1);   // monday
+	MM58174(config, m_mm58174, 32.768_kHz_XTAL);
 
 	/* via */
 	VIA6522(config, m_via0, 16.364_MHz_XTAL / 16);
diff --git a/src/mame/drivers/dmax8000.cpp b/src/mame/drivers/dmax8000.cpp
index b5e1f7b6797..cb2b1eaa797 100644
--- a/src/mame/drivers/dmax8000.cpp
+++ b/src/mame/drivers/dmax8000.cpp
@@ -31,7 +31,7 @@ What there is of the schematic shows no sign of a daisy chain or associated inte
 #include "machine/z80pio.h"
 #include "machine/z80sio.h"
 #include "machine/z80ctc.h"
-#include "machine/mm58274c.h"
+#include "machine/mm58174.h"
 #include "bus/rs232/rs232.h"
 
 
@@ -122,7 +122,7 @@ void dmax8000_state::dmax8000_io(address_map &map)
 	map(0x20, 0x23).rw("dart2", FUNC(z80dart_device::ba_cd_r), FUNC(z80dart_device::ba_cd_w));
 	map(0x40, 0x40).w(FUNC(dmax8000_state::port40_w)); // memory bank control
 	//map(0x60, 0x67) // optional IEEE488 GPIB
-	map(0x70, 0x7f).rw("rtc", FUNC(mm58274c_device::read), FUNC(mm58274c_device::write)); // optional RTC
+	map(0x70, 0x7f).rw("rtc", FUNC(mm58174_device::read), FUNC(mm58174_device::write)); // optional RTC
 }
 
 /* Input ports */
@@ -195,10 +195,7 @@ void dmax8000_state::dmax8000(machine_config &config)
 	m_fdc->drq_wr_callback().set(FUNC(dmax8000_state::fdc_drq_w));
 	FLOPPY_CONNECTOR(config, "fdc:0", floppies, "8dsdd", floppy_image_device::default_floppy_formats).enable_sound(true);
 
-	mm58274c_device &rtc(MM58274C(config, "rtc", 0)); // MM58174
-	// this is all guess
-	rtc.set_mode24(0); // 12 hour
-	rtc.set_day1(1);   // monday
+	MM58174(config, "rtc", 0);
 }
 
 
diff --git a/src/mame/drivers/gridcomp.cpp b/src/mame/drivers/gridcomp.cpp
index 6ae28c78fba..6647ce5859e 100644
--- a/src/mame/drivers/gridcomp.cpp
+++ b/src/mame/drivers/gridcomp.cpp
@@ -72,6 +72,7 @@
 #include "machine/i7220.h"
 #include "machine/i80130.h"
 #include "machine/i8255.h"
+#include "machine/mm58174.h"
 #include "machine/ram.h"
 #include "machine/tms9914.h"
 #include "machine/z80sio.h"
@@ -104,6 +105,7 @@ public:
 		: driver_device(mconfig, type, tag)
 		, m_maincpu(*this, "maincpu")
 		, m_osp(*this, I80130_TAG)
+		, m_rtc(*this, "rtc")
 		, m_modem(*this, "modem")
 		, m_uart8274(*this, "uart8274")
 		, m_speaker(*this, "speaker")
@@ -123,6 +125,7 @@ public:
 private:
 	required_device<cpu_device> m_maincpu;
 	required_device<i80130_device> m_osp;
+	required_device<mm58174_device> m_rtc;
 	required_device<i8255_device> m_modem;
 	optional_device<i8274_device> m_uart8274;
 	required_device<speaker_sound_device> m_speaker;
@@ -307,7 +310,7 @@ void gridcomp_state::grid1101_map(address_map &map)
 	map(0xdfea0, 0xdfeaf).unmaprw(); // ??
 	map(0xdfec0, 0xdfecf).rw(FUNC(gridcomp_state::grid_modem_r), FUNC(gridcomp_state::grid_modem_w)).umask16(0x00ff); // incl. DTMF generator
 	map(0xdff00, 0xdff1f).rw("uart8274", FUNC(i8274_device::ba_cd_r), FUNC(i8274_device::ba_cd_w)).umask16(0x00ff);
-	map(0xdff40, 0xdff5f).noprw();   // ?? machine ID EAROM, RTC
+	map(0xdff40, 0xdff5f).rw(m_rtc, FUNC(mm58174_device::read), FUNC(mm58174_device::write)).umask16(0xff00);
 	map(0xdff80, 0xdff8f).rw("hpib", FUNC(tms9914_device::read), FUNC(tms9914_device::write)).umask16(0x00ff);
 	map(0xdffc0, 0xdffcf).rw(FUNC(gridcomp_state::grid_keyb_r), FUNC(gridcomp_state::grid_keyb_w)); // Intel 8741 MCU
 	map(0xe0000, 0xeffff).rw(FUNC(gridcomp_state::grid_dma_r), FUNC(gridcomp_state::grid_dma_w)); // DMA
@@ -326,7 +329,7 @@ void gridcomp_state::grid1121_map(address_map &map)
 	map(0xdfe80, 0xdfe83).rw("i7220", FUNC(i7220_device::read), FUNC(i7220_device::write)).umask16(0x00ff);
 	map(0xdfea0, 0xdfeaf).unmaprw(); // ??
 	map(0xdfec0, 0xdfecf).rw(FUNC(gridcomp_state::grid_modem_r), FUNC(gridcomp_state::grid_modem_w)).umask16(0x00ff); // incl. DTMF generator
-	map(0xdff40, 0xdff5f).noprw();   // ?? machine ID EAROM, RTC
+	map(0xdff40, 0xdff5f).rw(m_rtc, FUNC(mm58174_device::read), FUNC(mm58174_device::write)).umask16(0xff00);
 	map(0xdff80, 0xdff8f).rw("hpib", FUNC(tms9914_device::read), FUNC(tms9914_device::write)).umask16(0x00ff);
 	map(0xdffc0, 0xdffcf).rw(FUNC(gridcomp_state::grid_keyb_r), FUNC(gridcomp_state::grid_keyb_w)); // Intel 8741 MCU
 	map(0xfc000, 0xfffff).rom().region("user1", 0);
@@ -363,6 +366,8 @@ void gridcomp_state::grid1101(machine_config &config)
 	I80130(config, m_osp, XTAL(15'000'000)/3);
 	m_osp->irq().set_inputline("maincpu", 0);
 
+	MM58174(config, m_rtc, 32.768_kHz_XTAL);
+
 	SPEAKER(config, "mono").front_center();
 	SPEAKER_SOUND(config, m_speaker).add_route(ALL_OUTPUTS, "mono", 1.00);
 
diff --git a/src/mame/drivers/m24.cpp b/src/mame/drivers/m24.cpp
index 2ddf54dcbd7..a955e07e0c8 100644
--- a/src/mame/drivers/m24.cpp
+++ b/src/mame/drivers/m24.cpp
@@ -30,7 +30,7 @@
 #include "machine/i8087.h"
 #include "machine/m24_kbd.h"
 #include "machine/m24_z8000.h"
-#include "machine/mm58274c.h"
+#include "machine/mm58174.h"
 #include "machine/pit8253.h"
 #include "machine/pic8259.h"
 #include "machine/ram.h"
@@ -460,7 +460,7 @@ void m24_state::m24_io(address_map &map)
 	map(0x0064, 0x0064).r(FUNC(m24_state::keyboard_status_r));
 	map(0x0065, 0x0065).w(FUNC(m24_state::alt_w));
 	map(0x0066, 0x0067).portr("DSW0");
-	map(0x0070, 0x007f).rw("mm58174an", FUNC(mm58274c_device::read), FUNC(mm58274c_device::write));
+	map(0x0070, 0x007f).rw("mm58174an", FUNC(mm58174_device::read), FUNC(mm58174_device::write));
 	map(0x0080, 0x0083).mirror(0xc).w(FUNC(m24_state::dma_segment_w));
 	map(0x00a0, 0x00a1).mirror(0xe).w(FUNC(m24_state::nmi_enable_w));
 	map(0x80c1, 0x80c1).rw(m_z8000_apb, FUNC(m24_z8000_device::handshake_r), FUNC(m24_z8000_device::handshake_w));
@@ -607,10 +607,7 @@ void m24_state::olivetti(machine_config &config)
 	M24_KEYBOARD(config, m_keyboard, 0);
 	m_keyboard->out_data_handler().set(FUNC(m24_state::kbcin_w));
 
-	mm58274c_device &mm58174an(MM58274C(config, "mm58174an", 32.768_kHz_XTAL));
-	// this is all guess
-	mm58174an.set_mode24(1); // ?
-	mm58174an.set_day1(1);   // ?
+	MM58174(config, "mm58174an", 32.768_kHz_XTAL);
 
 	M24_Z8000(config, m_z8000_apb, 0); // TODO: make this a slot device (uses custom bus connector)
 	m_z8000_apb->halt_callback().set(FUNC(m24_state::halt_i86_w));
diff --git a/src/mame/drivers/v6809.cpp b/src/mame/drivers/v6809.cpp
index 4e6f846bfef..d95fad28c8c 100644
--- a/src/mame/drivers/v6809.cpp
+++ b/src/mame/drivers/v6809.cpp
@@ -56,7 +56,7 @@ ToDo:
 #include "machine/6850acia.h"
 #include "machine/clock.h"
 #include "machine/keyboard.h"
-#include "machine/mm58274c.h"
+#include "machine/mm58174.h"
 #include "machine/wd_fdc.h"
 #include "sound/spkrdev.h"
 #include "video/mc6845.h"
@@ -128,7 +128,7 @@ void v6809_state::v6809_mem(address_map &map)
 	map(0xf500, 0xf501).mirror(0x36).rw("acia0", FUNC(acia6850_device::read), FUNC(acia6850_device::write)); // modem
 	map(0xf508, 0xf509).mirror(0x36).rw("acia1", FUNC(acia6850_device::read), FUNC(acia6850_device::write)); // printer
 	map(0xf600, 0xf603).mirror(0x3c).rw(m_fdc, FUNC(mb8876_device::read), FUNC(mb8876_device::write));
-	map(0xf640, 0xf64f).mirror(0x30).rw("rtc", FUNC(mm58274c_device::read), FUNC(mm58274c_device::write));
+	map(0xf640, 0xf64f).mirror(0x30).rw("rtc", FUNC(mm58174_device::read), FUNC(mm58174_device::write));
 	map(0xf680, 0xf683).mirror(0x3c).rw(m_pia0, FUNC(pia6821_device::read), FUNC(pia6821_device::write));
 	map(0xf6c0, 0xf6c7).mirror(0x08).rw("ptm", FUNC(ptm6840_device::read), FUNC(ptm6840_device::write));
 	map(0xf6d0, 0xf6d3).mirror(0x0c).rw("pia1", FUNC(pia6821_device::read), FUNC(pia6821_device::write));
@@ -343,10 +343,7 @@ void v6809_state::v6809(machine_config &config)
 	acia_clock.signal_handler().append("acia1", FUNC(acia6850_device::write_txc));
 	acia_clock.signal_handler().append("acia1", FUNC(acia6850_device::write_rxc));
 
-	mm58274c_device &rtc(MM58274C(config, "rtc", 0));
-// this is all guess
-	rtc.set_mode24(0); // 12 hour
-	rtc.set_day1(1);   // monday
+	MM58174(config, "rtc", 0);
 
 	MB8876(config, m_fdc, 16_MHz_XTAL / 16);
 	FLOPPY_CONNECTOR(config, "fdc:0", v6809_floppies, "525dd", floppy_image_device::default_floppy_formats).enable_sound(true);
diff --git a/src/mame/drivers/wicat.cpp b/src/mame/drivers/wicat.cpp
index 5f278ebfd75..eb39e74398c 100644
--- a/src/mame/drivers/wicat.cpp
+++ b/src/mame/drivers/wicat.cpp
@@ -28,7 +28,7 @@ Wicat - various systems.
 #include "machine/am9517a.h"
 #include "machine/im6402.h"
 #include "machine/input_merger.h"
-#include "machine/mm58274c.h"
+#include "machine/mm58174.h"
 #include "machine/scn_pci.h"
 #include "machine/wd_fdc.h"
 #include "machine/x2212.h"
@@ -92,7 +92,7 @@ private:
 	I8275_DRAW_CHARACTER_MEMBER(wicat_display_pixels);
 
 	required_device<m68000_device> m_maincpu;
-	required_device<mm58274c_device> m_rtc;
+	required_device<mm58174_device> m_rtc;
 	required_device<via6522_device> m_via;
 	required_device_array<scn2661c_device, 7> m_uart;
 	required_device<cpu_device> m_videocpu;
@@ -157,7 +157,7 @@ void wicat_state::main_mem(address_map &map)
 	map(0xf00030, 0xf00037).rw(m_uart[6], FUNC(scn2661c_device::read), FUNC(scn2661c_device::write)).umask16(0xff00);
 	map(0xf0003a, 0xf0003b).nopr();
 	map(0xf00040, 0xf0005f).rw(FUNC(wicat_state::via_r), FUNC(wicat_state::via_w));
-	map(0xf00060, 0xf0007f).rw(m_rtc, FUNC(mm58274c_device::read), FUNC(mm58274c_device::write)).umask16(0xff00);
+	map(0xf00060, 0xf0007f).rw(m_rtc, FUNC(mm58174_device::read), FUNC(mm58174_device::write)).umask16(0xff00);
 	map(0xf000d0, 0xf000d0).w("ledlatch", FUNC(ls259_device::write_nibble_d3));
 	map(0xf00180, 0xf0018f).rw(FUNC(wicat_state::hdc_r), FUNC(wicat_state::hdc_w));  // WD1000
 	map(0xf00190, 0xf0019f).rw(FUNC(wicat_state::fdc_r), FUNC(wicat_state::fdc_w));  // FD1795
@@ -644,9 +644,7 @@ void wicat_state::wicat(machine_config &config)
 	m_via->writepb_handler().set(FUNC(wicat_state::via_b_w));
 	m_via->irq_handler().set_inputline(m_maincpu, M68K_IRQ_1);
 
-	MM58274C(config, m_rtc, 0);  // actually an MM58174AN, but should be compatible
-	m_rtc->set_mode24(0); // 12 hour
-	m_rtc->set_day1(1);   // monday
+	MM58174(config, m_rtc, 0);
 
 	// internal terminal
 	SCN2661C(config, m_uart[0], 5.0688_MHz_XTAL);  // connected to terminal board
diff --git a/src/mame/includes/concept.h b/src/mame/includes/concept.h
index 3dd6b89f7dd..84d39e3f397 100644
--- a/src/mame/includes/concept.h
+++ b/src/mame/includes/concept.h
@@ -16,7 +16,7 @@
 #include "cpu/m68000/m68000.h"
 #include "machine/6522via.h"
 #include "machine/mos6551.h"
-#include "machine/mm58274c.h"   /* mm58274 seems to be compatible with mm58174 */
+#include "machine/mm58174.h"
 #include "sound/spkrdev.h"
 #include "bus/a2bus/a2bus.h"
 
@@ -36,7 +36,7 @@ public:
 		m_via0(*this, VIA_0_TAG),
 		m_kbdacia(*this, KBD_ACIA_TAG),
 		m_speaker(*this, "spkr"),
-		m_mm58274(*this,"mm58274c"),
+		m_mm58174(*this, "mm58174"),
 		m_a2bus(*this, "a2bus"),
 		m_videoram(*this,"videoram")
 	{ }
@@ -50,7 +50,7 @@ private:
 	required_device<via6522_device> m_via0;
 	required_device<mos6551_device> m_kbdacia;
 	required_device<speaker_sound_device> m_speaker;
-	required_device<mm58274c_device> m_mm58274;
+	required_device<mm58174_device> m_mm58174;
 	required_device<a2bus_device> m_a2bus;
 	required_shared_ptr<uint16_t> m_videoram;
 
diff --git a/src/mame/machine/concept.cpp b/src/mame/machine/concept.cpp
index b412ce093fd..4be4dbc15f9 100644
--- a/src/mame/machine/concept.cpp
+++ b/src/mame/machine/concept.cpp
@@ -224,7 +224,7 @@ READ8_MEMBER(concept_state::io_r)
 		/* calendar R/W */
 		VLOG(("concept_io_r: Calendar read at address 0x03%4.4x\n", offset << 1));
 		if (!m_clock_enable)
-			return m_mm58274->read(m_clock_address);
+			return m_mm58174->read(m_clock_address);
 		break;
 
 	case 7:
@@ -330,7 +330,7 @@ WRITE8_MEMBER(concept_state::io_w)
 		/* calendar R/W */
 		LOG(("concept_io_w: Calendar written to at address 0x03%4.4x, data: 0x%4.4x\n", offset << 1, data));
 		if (!m_clock_enable)
-			m_mm58274->write(m_clock_address, data & 0xf);
+			m_mm58174->write(m_clock_address, data & 0xf);
 		break;
 
 	case 7: