From dbcffd411f68c2879eda3ed949b34a3ed8348317 Mon Sep 17 00:00:00 2001
From: AJR <ajrhacker@users.noreply.github.com>
Date: Thu, 2 Jan 2020 23:10:54 -0500
Subject: [PATCH] mc68901: Sweeping rewrite of USART emulation (no longer based
 on device_serial_interface), adding support for 16x clock prescaler and data
 transition synchronization, break generation and detection, internal loopback
 and synchronous mode.

harriet, x68k_kbd: Adjust serial clocks to match MFP-generated baud rates.

indiana: Replace serial ASCII keyboard with AT-style keyboard (which only mostly works). Document some clocks and interrupts.

tti: Terminal actually works now.
---
 src/devices/machine/mc68901.cpp | 673 ++++++++++++++++++++++++--------
 src/devices/machine/mc68901.h   |  56 ++-
 src/mame/drivers/atarist.cpp    |  19 +-
 src/mame/drivers/harriet.cpp    |  20 +-
 src/mame/drivers/indiana.cpp    |  61 +--
 src/mame/drivers/micro3d.cpp    |   6 +-
 src/mame/drivers/tti.cpp        |   8 +-
 src/mame/drivers/x68k.cpp       |   7 +-
 src/mame/includes/atarist.h     |   3 -
 src/mame/machine/x68k_kbd.cpp   |   2 +-
 10 files changed, 611 insertions(+), 244 deletions(-)

diff --git a/src/devices/machine/mc68901.cpp b/src/devices/machine/mc68901.cpp
index fcb5f967dc4..3994a4863c6 100644
--- a/src/devices/machine/mc68901.cpp
+++ b/src/devices/machine/mc68901.cpp
@@ -1,9 +1,12 @@
 // license:BSD-3-Clause
-// copyright-holders:Curt Coder
+// copyright-holders:Curt Coder, AJR
 /**********************************************************************
 
     Motorola MC68901 Multi Function Peripheral emulation
 
+    This chip was originally designed by Mostek (MK68901) as a 68000-
+    oriented evolution of the Z80 STI.
+
 **********************************************************************/
 
 /*
@@ -34,12 +37,7 @@
         the GLUE is essentially invisible w.r.t IPL.  The CPU and the
         MFP manage to add the delays all by themselves.
 
-    - divide serial clock by 16
-    - synchronous mode
-    - 1.5/2 stop bits
-    - interrupt on receiver break end
-    - interrupt on character boundaries during break transmission
-    - loopback mode
+    - RR & TR outputs
 
 */
 
@@ -47,7 +45,11 @@
 #include "mc68901.h"
 #include "cpu/m68000/m68000.h"
 
-//#define VERBOSE 1
+#define LOG_GENERAL (1 << 0U)
+#define LOG_RCV     (1 << 1U)
+#define LOG_XMIT    (1 << 2U)
+
+//#define VERBOSE (LOG_GENERAL | LOG_RCV | LOG_XMIT)
 #include "logmacro.h"
 
 
@@ -196,6 +198,22 @@ inline void mc68901_device::take_interrupt(u16 mask)
 	check_interrupts();
 }
 
+inline void mc68901_device::tx_buffer_empty()
+{
+	if (m_ier & IR_XMIT_BUFFER_EMPTY)
+	{
+		take_interrupt(IR_XMIT_BUFFER_EMPTY);
+	}
+}
+
+inline void mc68901_device::tx_error()
+{
+	if (m_ier & IR_XMIT_ERROR)
+	{
+		take_interrupt(IR_XMIT_ERROR);
+	}
+}
+
 inline void mc68901_device::rx_buffer_full()
 {
 	if (m_ier & IR_RCV_BUFFER_FULL)
@@ -330,10 +348,7 @@ void mc68901_device::gpio_output()
 
 mc68901_device::mc68901_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
 	: device_t(mconfig, MC68901, tag, owner, clock),
-		device_serial_interface(mconfig, *this),
 		m_timer_clock(0),
-		m_rx_clock(0),
-		m_tx_clock(0),
 		m_out_irq_cb(*this),
 		m_out_gpio_cb(*this),
 		m_out_tao_cb(*this),
@@ -346,8 +361,28 @@ mc68901_device::mc68901_device(const machine_config &mconfig, const char *tag, d
 		m_iack_chain_cb(*this),
 		m_aer(0),
 		m_ier(0),
+		m_scr(0),
+		m_scr_parity(false),
+		m_transmit_buffer(0),
+		m_receive_buffer(0),
 		m_gpio_input(0),
-		m_gpio_output(0xff)
+		m_gpio_output(0xff),
+		m_rframe(0),
+		m_rclk(0),
+		m_rbits(0),
+		m_si_scan(0xff),
+		m_next_rsr(0),
+		m_rc(true),
+		m_si(true),
+		m_last_si(true),
+		m_rparity(false),
+		m_osr(0),
+		m_tclk(0),
+		m_tbits(0),
+		m_tc(true),
+		m_so(false),
+		m_tparity(false),
+		m_underrun(false)
 {
 }
 
@@ -358,8 +393,6 @@ mc68901_device::mc68901_device(const machine_config &mconfig, const char *tag, d
 
 void mc68901_device::device_start()
 {
-	m_start_bit_hack_for_external_clocks = true;
-
 	/* resolve callbacks */
 	m_out_irq_cb.resolve_safe();
 	m_out_gpio_cb.resolve_safe();
@@ -378,16 +411,6 @@ void mc68901_device::device_start()
 	m_timer[TIMER_C] = timer_alloc(TIMER_C);
 	m_timer[TIMER_D] = timer_alloc(TIMER_D);
 
-	if (m_rx_clock > 0)
-	{
-		set_rcv_rate(m_rx_clock);
-	}
-
-	if (m_tx_clock > 0)
-	{
-		set_tra_rate(m_tx_clock);
-	}
-
 	/* register for state saving */
 	save_item(NAME(m_gpip));
 	save_item(NAME(m_aer));
@@ -405,17 +428,30 @@ void mc68901_device::device_start()
 	save_item(NAME(m_to));
 	save_item(NAME(m_ti));
 	save_item(NAME(m_scr));
+	save_item(NAME(m_scr_parity));
 	save_item(NAME(m_ucr));
 	save_item(NAME(m_rsr));
 	save_item(NAME(m_tsr));
 	save_item(NAME(m_transmit_buffer));
-	save_item(NAME(m_transmit_pending));
 	save_item(NAME(m_receive_buffer));
-	save_item(NAME(m_overrun_pending));
 	save_item(NAME(m_gpio_input));
 	save_item(NAME(m_gpio_output));
-	save_item(NAME(m_rsr_read));
+	save_item(NAME(m_rframe));
+	save_item(NAME(m_rclk));
+	save_item(NAME(m_rbits));
+	save_item(NAME(m_si_scan));
 	save_item(NAME(m_next_rsr));
+	save_item(NAME(m_rc));
+	save_item(NAME(m_si));
+	save_item(NAME(m_last_si));
+	save_item(NAME(m_rparity));
+	save_item(NAME(m_osr));
+	save_item(NAME(m_tclk));
+	save_item(NAME(m_tbits));
+	save_item(NAME(m_tc));
+	save_item(NAME(m_so));
+	save_item(NAME(m_tparity));
+	save_item(NAME(m_underrun));
 }
 
 
@@ -425,13 +461,16 @@ void mc68901_device::device_start()
 
 void mc68901_device::device_reset()
 {
-	m_tsr = 0;
-	m_transmit_pending = false;
-	m_overrun_pending = false;
+	m_rsr = 0;
+	m_tsr = TSR_BUFFER_EMPTY;
+	m_underrun = false;
+	m_rclk = 0;
+	m_tclk = 0;
 
 	// Avoid read-before-write
 	m_ipr = m_imr = 0;
 
+	m_rframe = 0x100;
 	m_next_rsr = 0;
 
 	memset(m_tmc, 0, sizeof(m_tmc));
@@ -455,10 +494,8 @@ void mc68901_device::device_reset()
 	write(REGISTER_TCDCR, 0);
 	write(REGISTER_SCR, 0);
 	write(REGISTER_UCR, 0);
-	write(REGISTER_RSR, 0);
 
-	transmit_register_reset();
-	receive_register_reset();
+	set_so(true);
 }
 
 
@@ -474,84 +511,7 @@ void mc68901_device::device_timer(emu_timer &timer, device_timer_id id, int para
 
 
 //-------------------------------------------------
-//  tra_callback -
-//-------------------------------------------------
-
-void mc68901_device::tra_callback()
-{
-	m_out_so_cb(transmit_register_get_data_bit());
-}
-
-
-//-------------------------------------------------
-//  tra_complete -
-//-------------------------------------------------
-
-void mc68901_device::tra_complete()
-{
-	if (m_tsr & TSR_XMIT_ENABLE)
-	{
-		if (m_transmit_pending)
-		{
-			transmit_register_setup(m_transmit_buffer);
-			m_transmit_pending = false;
-			m_tsr |= TSR_BUFFER_EMPTY;
-
-			if (m_ier & IR_XMIT_BUFFER_EMPTY)
-			{
-				take_interrupt(IR_XMIT_BUFFER_EMPTY);
-			}
-		}
-		else
-		{
-			m_tsr |= TSR_UNDERRUN_ERROR;
-			// TODO: transmit error?
-		}
-	}
-	else
-	{
-		m_tsr |= TSR_END_OF_XMIT;
-	}
-}
-
-
-//-------------------------------------------------
-//  rcv_complete -
-//-------------------------------------------------
-
-void mc68901_device::rcv_complete()
-{
-	receive_register_extract();
-	if (m_rsr & RSR_BUFFER_FULL)
-	{
-		m_overrun_pending = true;
-	}
-	else
-	{
-		m_receive_buffer = get_received_char();
-		m_rsr |= RSR_BUFFER_FULL;
-		LOG("Received Character: %02x\n", m_receive_buffer);
-
-		if (is_receive_framing_error())
-			m_rsr |= RSR_FRAME_ERROR;
-		else
-			m_rsr &= ~RSR_FRAME_ERROR;
-
-		if (is_receive_parity_error())
-			m_rsr |= RSR_PARITY_ERROR;
-		else
-			m_rsr &= ~RSR_PARITY_ERROR;
-
-		if ((m_rsr & (RSR_FRAME_ERROR | RSR_PARITY_ERROR)) && (m_ier & IR_RCV_ERROR))
-			rx_error();
-		else
-			rx_buffer_full();
-	}
-}
-
-
-//-------------------------------------------------
-//  read -
+//  read - read from one MFP register
 //-------------------------------------------------
 
 u8 mc68901_device::read(offs_t offset)
@@ -595,7 +555,7 @@ u8 mc68901_device::read(offs_t offset)
 		{
 			/* clear UE bit (in reality, this won't be cleared until one full clock cycle of the transmitter has passed since the bit was set) */
 			u8 tsr = m_tsr;
-			if (!machine().side_effects_disabled())
+			if (!machine().side_effects_disabled() && !m_underrun)
 				m_tsr &= ~TSR_UNDERRUN_ERROR;
 			return tsr;
 		}
@@ -604,10 +564,15 @@ u8 mc68901_device::read(offs_t offset)
 		if (!machine().side_effects_disabled())
 		{
 			m_rsr &= ~RSR_BUFFER_FULL;
-			if (m_overrun_pending)
+			if (m_next_rsr != 0)
 			{
-				m_overrun_pending = false;
-				m_rsr |= RSR_OVERRUN_ERROR;
+				m_rsr |= m_next_rsr;
+				m_next_rsr = 0;
+				rx_error();
+			}
+			if ((m_rsr & RSR_BREAK) && BIT(m_rframe, 9))
+			{
+				m_rsr &= ~RSR_BREAK;
 				rx_error();
 			}
 		}
@@ -620,7 +585,7 @@ u8 mc68901_device::read(offs_t offset)
 
 
 //-------------------------------------------------
-//  write -
+//  write - write to one MFP register
 //-------------------------------------------------
 
 void mc68901_device::write(offs_t offset, u8 data)
@@ -917,6 +882,7 @@ void mc68901_device::write(offs_t offset, u8 data)
 		LOG("MC68901 Sync Character : %x\n", data);
 
 		m_scr = data;
+		m_scr_parity = BIT(population_count_32(data), 0);
 		break;
 
 	case REGISTER_UCR:
@@ -931,60 +897,41 @@ void mc68901_device::write(offs_t offset, u8 data)
 		case UCR_WORD_LENGTH_5: data_bit_count = 5; break;
 		}
 
-		parity_t parity;
-
 		if (data & UCR_PARITY_ENABLED)
 		{
 			if (data & UCR_PARITY_EVEN)
 			{
 				LOG("MC68901 Parity : Even\n");
-
-				parity = PARITY_EVEN;
 			}
 			else
 			{
 				LOG("MC68901 Parity : Odd\n");
-
-				parity = PARITY_ODD;
 			}
 		}
 		else
 		{
 			LOG("MC68901 Parity : Disabled\n");
-
-			parity = PARITY_NONE;
 		}
 
 		LOG("MC68901 Word Length : %u bits\n", data_bit_count);
 
 
-		int start_bits;
-		stop_bits_t stop_bits;
-
 		switch (data & 0x18)
 		{
 		case UCR_START_STOP_0_0:
 		default:
-			start_bits = 0;
-			stop_bits = STOP_BITS_0;
 			LOG("MC68901 Start Bits : 0, Stop Bits : 0, Format : synchronous\n");
 			break;
 
 		case UCR_START_STOP_1_1:
-			start_bits = 1;
-			stop_bits = STOP_BITS_1;
 			LOG("MC68901 Start Bits : 1, Stop Bits : 1, Format : asynchronous\n");
 			break;
 
 		case UCR_START_STOP_1_15:
-			start_bits = 1;
-			stop_bits = STOP_BITS_1_5;
 			LOG("MC68901 Start Bits : 1, Stop Bits : 1.5, Format : asynchronous\n");
 			break;
 
 		case UCR_START_STOP_1_2:
-			start_bits = 1;
-			stop_bits = STOP_BITS_2;
 			LOG("MC68901 Start Bits : 1, Stop Bits : 2, Format : asynchronous\n");
 			break;
 		}
@@ -998,9 +945,6 @@ void mc68901_device::write(offs_t offset, u8 data)
 			LOG("MC68901 Rx/Tx Clock Divisor : 1\n");
 		}
 
-		set_data_frame(start_bits, data_bit_count, parity, stop_bits);
-		receive_register_reset();
-
 		m_ucr = data;
 		}
 		break;
@@ -1014,20 +958,32 @@ void mc68901_device::write(offs_t offset, u8 data)
 		else
 		{
 			LOG("MC68901 Receiver Enabled\n");
+			m_rsr |= RSR_RCV_ENABLE;
 
 			if (data & RSR_SYNC_STRIP_ENABLE)
 			{
 				LOG("MC68901 Sync Strip Enabled\n");
+				m_rsr |= RSR_SYNC_STRIP_ENABLE;
 			}
 			else
 			{
 				LOG("MC68901 Sync Strip Disabled\n");
+				m_rsr &= ~RSR_SYNC_STRIP_ENABLE;
 			}
 
-			if (data & RSR_FOUND_SEARCH)
-				LOG("MC68901 Receiver Search Mode Enabled\n");
-
-			m_rsr = data & 0x0b;
+			if ((m_ucr & UCR_START_STOP_1_2) == UCR_START_STOP_0_0)
+			{
+				if (data & RSR_FOUND_SEARCH)
+				{
+					LOG("MC68901 Receiver Search Mode Disabled\n");
+					m_rsr |= RSR_FOUND_SEARCH;
+				}
+				else
+				{
+					LOG("MC68901 Receiver Search Mode Disabled\n");
+					m_rsr &= ~RSR_FOUND_SEARCH;
+				}
+			}
 		}
 		break;
 
@@ -1036,12 +992,11 @@ void mc68901_device::write(offs_t offset, u8 data)
 
 		if ((data & TSR_XMIT_ENABLE) == 0)
 		{
-			LOG("MC68901 Transmitter Disabled\n");
-
 			m_tsr &= ~TSR_UNDERRUN_ERROR;
+			m_underrun = false;
 
-			if (is_transmit_register_empty())
-				m_tsr |= TSR_END_OF_XMIT;
+			if (m_tbits == 0)
+				set_so((m_tsr & TSR_OUTPUT_MASK) != TSR_OUTPUT_LOW);
 		}
 		else
 		{
@@ -1082,29 +1037,13 @@ void mc68901_device::write(offs_t offset, u8 data)
 			}
 
 			m_tsr &= ~TSR_END_OF_XMIT;
-
-			if (m_transmit_pending && is_transmit_register_empty())
-			{
-				transmit_register_setup(m_transmit_buffer);
-				m_transmit_pending = false;
-			}
-			if (!m_transmit_pending)
-				m_tsr |= TSR_BUFFER_EMPTY;
 		}
 		break;
 
 	case REGISTER_UDR:
 		LOG("MC68901 UDR %x\n", data);
 		m_transmit_buffer = data;
-		m_transmit_pending = true;
 		m_tsr &= ~TSR_BUFFER_EMPTY;
-
-		if ((m_tsr & TSR_XMIT_ENABLE) && is_transmit_register_empty())
-		{
-			transmit_register_setup(m_transmit_buffer);
-			m_transmit_pending = false;
-			m_tsr |= TSR_BUFFER_EMPTY;
-		}
 		break;
 	}
 }
@@ -1161,7 +1100,413 @@ WRITE_LINE_MEMBER( mc68901_device::tbi_w )
 	timer_input(TIMER_B, state);
 }
 
-WRITE_LINE_MEMBER(mc68901_device::write_rx)
+//**************************************************************************
+//  USART
+//**************************************************************************
+
+//-------------------------------------------------
+//  si_w - serial data input for receiver
+//-------------------------------------------------
+
+WRITE_LINE_MEMBER(mc68901_device::si_w)
 {
-	device_serial_interface::rx_w(state);
+	m_si = state;
+}
+
+//-------------------------------------------------
+//  rc_w - receiver clock input
+//-------------------------------------------------
+
+WRITE_LINE_MEMBER(mc68901_device::rc_w)
+{
+	if (state != m_rc)
+	{
+		// receiver active on rising edge
+		m_rc = state;
+		if (state && (m_rsr & RSR_RCV_ENABLE) && (m_tsr & TSR_OUTPUT_MASK) != TSR_OUTPUT_LOOP)
+			rx_clock(m_si);
+	}
+}
+
+//-------------------------------------------------
+//  tc_w - transmitter clock input
+//-------------------------------------------------
+
+WRITE_LINE_MEMBER(mc68901_device::tc_w)
+{
+	if (state != m_tc)
+	{
+		// transmitter active on falling edge
+		m_tc = state;
+		if (!state && ((m_tsr & TSR_XMIT_ENABLE) || !(m_tsr & TSR_END_OF_XMIT)))
+			tx_clock();
+		else if (state && (m_rsr & RSR_RCV_ENABLE) && (m_tsr & TSR_OUTPUT_MASK) == TSR_OUTPUT_LOOP)
+			rx_clock(m_so);
+	}
+}
+
+//-------------------------------------------------
+//  set_so - set serial output
+//-------------------------------------------------
+
+void mc68901_device::set_so(bool state)
+{
+	if (m_so != state)
+	{
+		m_so = state;
+		m_out_so_cb(state);
+	}
+}
+
+//-------------------------------------------------
+//  rx_frame_start - begin a new frame of received
+//  data (following start bit for async mode)
+//-------------------------------------------------
+
+void mc68901_device::rx_frame_start()
+{
+	m_rframe = 0;
+	m_rbits = (m_ucr & UCR_WORD_LENGTH_MASK) >> 5;
+	m_rparity = (m_ucr & UCR_PARITY_EVEN) == UCR_PARITY_ODD;
+}
+
+//-------------------------------------------------
+//  rx_sync_found - notify that a sync character
+//  was found
+//-------------------------------------------------
+
+void mc68901_device::rx_sync_found()
+{
+	m_rsr |= RSR_FOUND_SEARCH;
+	LOGMASKED(LOG_RCV, "USART sync character found (%02X)\n", m_scr);
+
+	// causes error interrupt, but does not fill receiver buffer
+	rx_error();
+}
+
+//-------------------------------------------------
+//  rx_async_frame_complete - finish receiving one
+//  character in asynchronous mode
+//-------------------------------------------------
+
+void mc68901_device::rx_async_frame_complete()
+{
+	if (m_rsr & RSR_BUFFER_FULL)
+	{
+		LOGMASKED(LOG_RCV, "USART discarding received character %02X (%s)\n", m_rframe & 0xff, (m_rframe == 0 && !m_last_si) ? "break" : "overrun");
+		m_next_rsr |= (m_rframe == 0 && !m_last_si) ? RSR_BREAK : RSR_OVERRUN_ERROR;
+	}
+	else if (m_rsr & RSR_OVERRUN_ERROR)
+	{
+		if (m_rframe == 0 && !m_last_si)
+			m_rsr |= RSR_BREAK;
+	}
+	else
+	{
+		// load the receiver buffer
+		m_receive_buffer = m_rframe & 0xff;
+		m_rsr |= RSR_BUFFER_FULL;
+
+		// set error flags
+		m_rsr &= ~(RSR_PARITY_ERROR | RSR_FRAME_ERROR | RSR_BREAK);
+		if (m_rparity)
+			m_rsr |= RSR_PARITY_ERROR;
+		if (!m_last_si)
+			m_rsr |= m_rframe == 0 ? RSR_BREAK : RSR_FRAME_ERROR;
+		LOGMASKED(LOG_RCV, "USART received character: %02X (PE = %d, FE = %d, B = %d)\n", m_receive_buffer,
+			m_rparity,
+			!m_last_si && m_rframe != 0,
+			 !m_last_si && m_rframe == 0);
+
+		// set normal or error interrupt (if the latter is disabled, always use the former)
+		if ((m_rparity || !m_last_si) && (m_ier & IR_RCV_ERROR))
+			rx_error();
+		else
+			rx_buffer_full();
+	}
+}
+
+//-------------------------------------------------
+//  rx_sync_frame_complete - finish receiving one
+//  character in synchronous mode (error flags are
+//  different from asynchronous mode)
+//-------------------------------------------------
+
+void mc68901_device::rx_sync_frame_complete()
+{
+	// check if sync character matches
+	bool match = (m_rframe & 0xff) == (m_scr & (0xff >> ((m_ucr & UCR_WORD_LENGTH_MASK) >> 5))) && !m_rparity;
+
+	// suppress sync characters if strip option set
+	if (!match || !(m_rsr & RSR_SYNC_STRIP_ENABLE))
+	{
+		if (m_rsr & RSR_BUFFER_FULL)
+			m_next_rsr |= RSR_OVERRUN_ERROR;
+		else if (!(m_rsr & RSR_OVERRUN_ERROR))
+		{
+			// load the receiver buffer
+			m_receive_buffer = m_rframe & 0xff;
+			m_rsr |= RSR_BUFFER_FULL;
+
+			// set error flags
+			m_rsr &= ~(RSR_FRAME_ERROR | RSR_PARITY_ERROR | RSR_MATCH);
+			if (m_rparity)
+				m_rsr |= RSR_PARITY_ERROR;
+			if (match)
+				m_rsr |= RSR_MATCH;
+			LOGMASKED(LOG_RCV, "USART received character: %02X (PE = %d, sync %smatched)\n", m_receive_buffer,
+				m_rparity,
+				match ? "not " : "");
+
+			// set normal or error interrupt (if the latter is disabled, always use the former)
+			if ((m_rparity || match) && (m_ier & IR_RCV_ERROR))
+				rx_error();
+			else
+				rx_buffer_full();
+		}
+	}
+	else
+		LOGMASKED(LOG_RCV, "USART sync character stripped (%02X)\n", m_rframe & 0xff);
+}
+
+//-------------------------------------------------
+//  rx_clock - process one active transition on
+//  the receiver clock
+//-------------------------------------------------
+
+void mc68901_device::rx_clock(bool si)
+{
+	m_rclk++;
+	if (m_rclk >= 244)
+		m_rclk &= 15;
+	m_si_scan = (m_si_scan >> 1) | (si ? 0x80 : 0);
+	bool rclk_sync = (m_ucr & UCR_CLOCK_DIVIDE_16) == UCR_CLOCK_DIVIDE_1 || (m_rclk >= 4 && (m_si_scan & 0xe0) == (m_last_si ? 0 : 0xe0));
+	bool sync_mode = (m_ucr & UCR_START_STOP_1_2) == UCR_START_STOP_0_0;
+	if (rclk_sync)
+	{
+		LOGMASKED(LOG_RCV, "SI = %d (synchronized); RSR = %02X; rframe = %X; %d rbits, %d rclks\n", si, m_rsr, m_rframe, m_rbits, m_rclk);
+		m_last_si = si;
+		if (si && !sync_mode && !(m_rsr & RSR_CHAR_IN_PROGRESS))
+		{
+			m_rframe = 0x100;
+			if (!(m_rsr & RSR_BUFFER_FULL) && (m_rsr & RSR_BREAK))
+			{
+				// valid 0 to 1 transition ends break condition
+				m_rsr &= ~RSR_BREAK;
+				rx_error();
+			}
+		}
+		m_rclk = 0;
+	}
+
+	if ((m_ucr & UCR_CLOCK_DIVIDE_16) == UCR_CLOCK_DIVIDE_1 || (m_rclk & 15) == 8)
+	{
+		if (sync_mode && !(m_rsr & RSR_FOUND_SEARCH))
+		{
+			// search mode: continuous comparison
+			m_rframe = (m_rframe >> 1) | (m_last_si ? 0x100 : 0);
+			if ((m_ucr & UCR_PARITY_ENABLED) && (m_ucr & UCR_WORD_LENGTH_MASK) == UCR_WORD_LENGTH_8)
+			{
+				// check calculated parity of 8-bit sync character
+				if ((m_rframe & 0xff) == m_scr && m_last_si == ((m_ucr & UCR_PARITY_EVEN) ? m_scr_parity : !m_scr_parity))
+				{
+					rx_sync_found();
+					rx_frame_start();
+				}
+			}
+			else
+			{
+				// parity, if any, must be included in SCR when words are less than 8 bits
+				int frame_bits = ((m_ucr & UCR_PARITY_ENABLED) ? 9 : 8) - ((m_ucr & UCR_WORD_LENGTH_MASK) >> 5);
+				if ((m_rframe >> (9 - frame_bits)) == (m_scr & ((1 << frame_bits) - 1)))
+				{
+					rx_sync_found();
+					rx_frame_start();
+				}
+			}
+		}
+		else if (sync_mode || (m_rsr & RSR_CHAR_IN_PROGRESS))
+		{
+			if (m_rbits > 8)
+			{
+				rx_async_frame_complete();
+				m_rframe = m_last_si ? 0x100 : 0;
+				m_rsr &= ~RSR_CHAR_IN_PROGRESS;
+			}
+			else
+			{
+				LOGMASKED(LOG_RCV, "USART shifting in %d %s bit\n", m_last_si, m_rbits < 8 ? "data" : "parity");
+				m_rframe = (m_rframe >> 1) | (m_last_si ? 0x100 : 0);
+				if (m_last_si)
+					m_rparity = !m_rparity;
+				m_rbits++;
+
+				if (m_rbits == 8)
+				{
+					// adjust for fewer than 8 data bits
+					m_rframe >>= (m_ucr & UCR_WORD_LENGTH_MASK) >> 5;
+
+					// adjust for no parity
+					if (!(m_ucr & UCR_PARITY_ENABLED))
+					{
+						m_rframe >>= 1;
+						m_rparity = false;
+						m_rbits++;
+					}
+				}
+
+				if (m_rbits > 8 && sync_mode)
+				{
+					rx_sync_frame_complete();
+
+					// one character follows another in sync mode
+					rx_frame_start();
+				}
+			}
+		}
+		else if (!m_last_si && BIT(m_rframe, 8))
+		{
+			// start bit valid
+			LOGMASKED(LOG_RCV, "USART received start bit\n");
+			m_rsr |= RSR_CHAR_IN_PROGRESS;
+			rx_frame_start();
+		}
+	}
+}
+
+//-------------------------------------------------
+//  tx_frame_load - load one character into the
+//  shift register for transmission
+//-------------------------------------------------
+
+void mc68901_device::tx_frame_load(u8 data)
+{
+	// set up output shift register
+	m_osr = data;
+	m_tbits = 9 - ((m_ucr & UCR_WORD_LENGTH_MASK) >> 5);
+	m_tparity = (m_ucr & UCR_PARITY_EVEN) == UCR_PARITY_ODD;
+
+	// add start and stop bits for asynchronous mode
+	if ((m_ucr & UCR_START_STOP_1_2) != UCR_START_STOP_0_0)
+	{
+		m_osr = (m_osr << 1) | (1 << m_tbits);
+		m_tbits += 2;
+	}
+}
+
+//-------------------------------------------------
+//  tx_clock - process one active edge on the
+//  transmitter clock
+//-------------------------------------------------
+
+void mc68901_device::tx_clock()
+{
+	if (m_tclk != 0)
+	{
+		m_tclk--;
+		return;
+	}
+
+	m_underrun = false;
+
+	bool sync_mode = (m_ucr & UCR_START_STOP_1_2) == UCR_START_STOP_0_0;
+	if (m_tbits == (sync_mode ? 2 : 3))
+	{
+		// inject the calculated parity or skip that bit
+		if (m_ucr & UCR_PARITY_ENABLED)
+			m_osr = (m_osr << 1) | m_tparity;
+		else
+			m_tbits--;
+	}
+
+	bool send_break = !sync_mode && (m_tsr & TSR_BREAK);
+	bool tbusy = false;
+	if (m_tbits != 0)
+	{
+		m_tbits--;
+		if (m_tbits != 0)
+			tbusy = true;
+		else if (!(m_tsr & TSR_XMIT_ENABLE))
+		{
+			LOGMASKED(LOG_XMIT, "USART transmitter disabled\n");
+
+			// transmitter is now effectively disabled
+			m_tsr |= TSR_END_OF_XMIT;
+			tx_error();
+
+			// automatic turnaround enables the receiver
+			if (m_tsr & TSR_AUTO_TURNAROUND)
+				m_rsr |= RSR_RCV_ENABLE;
+		}
+		else if ((m_tsr & TSR_BUFFER_EMPTY) && !(m_tsr & TSR_UNDERRUN_ERROR) && !send_break)
+		{
+			LOGMASKED(LOG_XMIT, "USART transmitter underrun\n");
+
+			// underrun error condition
+			m_tsr |= TSR_UNDERRUN_ERROR;
+			m_underrun = true;
+			tx_error();
+		}
+	}
+
+	if (!tbusy && (m_tsr & TSR_XMIT_ENABLE))
+	{
+		// break inhibits reload
+		if (!(m_tsr & TSR_BUFFER_EMPTY) && !send_break)
+		{
+			LOGMASKED(LOG_XMIT, "USART loading character (%02X)\n", m_transmit_buffer);
+
+			// empty buffer into shift register
+			m_tsr |= TSR_BUFFER_EMPTY;
+			tx_buffer_empty();
+			tx_frame_load(m_transmit_buffer);
+			tbusy = true;
+		}
+		else if (sync_mode)
+		{
+			LOGMASKED(LOG_XMIT, "USART loading sync character (%02X)\n", m_scr);
+
+			// transmit sync characters if nothing else is loaded
+			tx_frame_load(m_scr);
+			tbusy = true;
+		}
+	}
+
+	if (tbusy)
+	{
+		LOGMASKED(LOG_XMIT, "USART shifting out %d %s bit\n", BIT(m_osr, 0),
+			m_tbits == 1 && !sync_mode ? "stop" : m_tbits == (sync_mode ? 1 : 2) ? "parity" : "data or start");
+
+		// shift out one bit
+		set_so(BIT(m_osr, 0));
+		if (BIT(m_osr, 0))
+			m_tparity = !m_tparity;
+		m_osr >>= 1;
+
+		if (m_tbits == 1 && (m_ucr & UCR_START_STOP_1_2) >= UCR_START_STOP_1_15)
+		{
+			// 1½ or 2 stop bits selected
+			if (m_ucr & UCR_CLOCK_DIVIDE_16)
+				m_tclk = (m_ucr & UCR_START_STOP_1_2) == UCR_START_STOP_1_2 ? 31 : 23;
+			else
+				m_tclk = (m_ucr & UCR_START_STOP_1_2) == UCR_START_STOP_1_2 ? 1 : 0;
+		}
+		else if (m_ucr & UCR_CLOCK_DIVIDE_16)
+			m_tclk = 15;
+	}
+	else if (!(m_tsr & TSR_XMIT_ENABLE))
+	{
+		// high/low output on SO (Hi-Z not supported)
+		set_so((m_tsr & TSR_OUTPUT_MASK) != TSR_OUTPUT_LOW);
+	}
+	else if (send_break)
+	{
+		set_so(false);
+		m_tbits = 1;
+	}
+	else
+	{
+		// asynchronous marking condition
+		set_so(true);
+	}
 }
diff --git a/src/devices/machine/mc68901.h b/src/devices/machine/mc68901.h
index 2199cb434e9..cc792b34900 100644
--- a/src/devices/machine/mc68901.h
+++ b/src/devices/machine/mc68901.h
@@ -1,5 +1,5 @@
 // license:BSD-3-Clause
-// copyright-holders:Curt Coder
+// copyright-holders:Curt Coder, AJR
 /**********************************************************************
 
     Motorola MC68901 Multi Function Peripheral emulation
@@ -38,8 +38,6 @@
 
 #pragma once
 
-#include "diserial.h"
-
 
 //**************************************************************************
 //  TYPE DEFINITIONS
@@ -48,19 +46,14 @@
 
 // ======================> mc68901_device
 
-class mc68901_device :  public device_t,
-						public device_serial_interface
+class mc68901_device :  public device_t
 {
 public:
 	// construction/destruction
 	mc68901_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
 
 	void set_timer_clock(int timer_clock) { m_timer_clock = timer_clock; }
-	void set_rx_clock(int rx_clock) { m_rx_clock = rx_clock; }
-	void set_tx_clock(int tx_clock) { m_tx_clock = tx_clock; }
 	void set_timer_clock(const XTAL &xtal) { set_timer_clock(xtal.value()); }
-	void set_rx_clock(const XTAL &xtal) { set_rx_clock(xtal.value()); }
-	void set_tx_clock(const XTAL &xtal) { set_tx_clock(xtal.value()); }
 
 	auto out_irq_cb() { return m_out_irq_cb.bind(); }
 	auto out_gpio_cb() { return m_out_gpio_cb.bind(); }
@@ -90,7 +83,9 @@ public:
 	DECLARE_WRITE_LINE_MEMBER( tai_w );
 	DECLARE_WRITE_LINE_MEMBER( tbi_w );
 
-	DECLARE_WRITE_LINE_MEMBER( write_rx );
+	DECLARE_WRITE_LINE_MEMBER( si_w );
+	DECLARE_WRITE_LINE_MEMBER( rc_w );
+	DECLARE_WRITE_LINE_MEMBER( tc_w );
 
 protected:
 	// device-level overrides
@@ -98,13 +93,10 @@ protected:
 	virtual void device_reset() override;
 	virtual void device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr) override;
 
-	// device_serial_interface overrides
-	virtual void tra_callback() override;
-	virtual void tra_complete() override;
-	virtual void rcv_complete() override;
-
 	void check_interrupts();
 	void take_interrupt(u16 mask);
+	void tx_buffer_empty();
+	void tx_error();
 	void rx_buffer_full();
 	void rx_error();
 	void timer_count(int index);
@@ -112,6 +104,15 @@ protected:
 	void gpio_input(int bit, int state);
 	void gpio_output();
 
+	void set_so(bool state);
+	void rx_frame_start();
+	void rx_sync_found();
+	void rx_async_frame_complete();
+	void rx_sync_frame_complete();
+	void rx_clock(bool si);
+	void tx_frame_load(u8 data);
+	void tx_clock();
+
 private:
 	enum
 	{
@@ -204,8 +205,6 @@ private:
 	static const int PRESCALER[];
 
 	int m_timer_clock;      /* timer clock */
-	int m_rx_clock;         /* serial receive clock */
-	int m_tx_clock;         /* serial transmit clock */
 
 	devcb_write_line        m_out_irq_cb;
 
@@ -239,13 +238,12 @@ private:
 	u8 m_tdr[4];                    // timer data registers
 
 	u8 m_scr;                       // synchronous character register
+	bool m_scr_parity;              // parity of sync character
 	u8 m_ucr;                       // USART control register
 	u8 m_tsr;                       // transmitter status register
 	u8 m_rsr;                       // receiver status register
 	u8 m_transmit_buffer;           // USART data register
-	bool m_transmit_pending;
 	u8 m_receive_buffer;
-	bool m_overrun_pending;
 	u8 m_gpio_input;
 	u8 m_gpio_output;
 
@@ -254,9 +252,25 @@ private:
 	int m_ti[4];                    // timer in latch
 	int m_to[4];                    // timer out latch
 
-	// serial state
+	// serial receiver state
+	u16 m_rframe;                   // receiver frame shift register
+	u8 m_rclk;                      // receiver clock counter
+	u8 m_rbits;                     // receiver bit counter
+	u8 m_si_scan;                   // receiver bitstream scan
 	u8 m_next_rsr;                  // receiver status register latch
-	int m_rsr_read;                 // receiver status register read flag
+	bool m_rc;                      // receiver clock input
+	bool m_si;                      // serial data input
+	bool m_last_si;                 // synchronized serial data input
+	bool m_rparity;                 // receiver data parity
+
+	// serial transmitter state
+	u16 m_osr;                      // output shift register
+	u8 m_tclk;                      // transmit clock counter
+	u8 m_tbits;                     // transmit bit counter
+	bool m_tc;                      // transmit clock input
+	bool m_so;                      // serial data output
+	bool m_tparity;                 // transmit data transmit
+	bool m_underrun;                // underrun preset time
 
 	// timers
 	emu_timer *m_timer[4];          // counter timers
diff --git a/src/mame/drivers/atarist.cpp b/src/mame/drivers/atarist.cpp
index 13c67039f01..27b3fd6b514 100644
--- a/src/mame/drivers/atarist.cpp
+++ b/src/mame/drivers/atarist.cpp
@@ -1780,11 +1780,6 @@ WRITE_LINE_MEMBER(st_state::write_acia_clock)
 }
 
 
-WRITE_LINE_MEMBER( st_state::mfp_tdo_w )
-{
-	m_mfp->clock_w(state);
-}
-
 WRITE_LINE_MEMBER( st_state::fdc_drq_w )
 {
 	if (state && (!(m_fdc_mode & DMA_MODE_ENABLED)) && (m_fdc_mode & DMA_MODE_FDC_HDC_ACK))
@@ -2019,14 +2014,13 @@ void st_state::common(machine_config &config)
 
 	MC68901(config, m_mfp, Y2/8);
 	m_mfp->set_timer_clock(Y1);
-	m_mfp->set_rx_clock(0);
-	m_mfp->set_tx_clock(0);
 	m_mfp->out_irq_cb().set_inputline(m_maincpu, M68K_IRQ_6);
-	m_mfp->out_tdo_cb().set(FUNC(st_state::mfp_tdo_w));
+	m_mfp->out_tdo_cb().set(m_mfp, FUNC(mc68901_device::tc_w));
+	m_mfp->out_tdo_cb().append(m_mfp, FUNC(mc68901_device::rc_w));
 	m_mfp->out_so_cb().set(m_rs232, FUNC(rs232_port_device::write_txd));
 
 	RS232_PORT(config, m_rs232, default_rs232_devices, nullptr);
-	m_rs232->rxd_handler().set(m_mfp, FUNC(mc68901_device::write_rx));
+	m_rs232->rxd_handler().set(m_mfp, FUNC(mc68901_device::si_w));
 	m_rs232->dcd_handler().set(m_mfp, FUNC(mc68901_device::i1_w));
 	m_rs232->cts_handler().set(m_mfp, FUNC(mc68901_device::i2_w));
 	m_rs232->ri_handler().set(m_mfp, FUNC(mc68901_device::i6_w));
@@ -2224,10 +2218,9 @@ void stbook_state::stbook(machine_config &config)
 
 	MC68901(config, m_mfp, U517/8);
 	m_mfp->set_timer_clock(Y1);
-	m_mfp->set_rx_clock(0);
-	m_mfp->set_tx_clock(0);
 	m_mfp->out_irq_cb().set_inputline(M68000_TAG, M68K_IRQ_6);
-	m_mfp->out_tdo_cb().set(FUNC(st_state::mfp_tdo_w));
+	m_mfp->out_tdo_cb().set(m_mfp, FUNC(mc68901_device::tc_w));
+	m_mfp->out_tdo_cb().append(m_mfp, FUNC(mc68901_device::rc_w));
 	m_mfp->out_so_cb().set(RS232_TAG, FUNC(rs232_port_device::write_txd));
 
 	WD1772(config, m_fdc, U517/2);
@@ -2243,7 +2236,7 @@ void stbook_state::stbook(machine_config &config)
 	m_centronics->set_output_latch(cent_data_out);
 
 	RS232_PORT(config, m_rs232, default_rs232_devices, nullptr);
-	m_rs232->rxd_handler().set(m_mfp, FUNC(mc68901_device::write_rx));
+	m_rs232->rxd_handler().set(m_mfp, FUNC(mc68901_device::si_w));
 	m_rs232->dcd_handler().set(m_mfp, FUNC(mc68901_device::i1_w));
 	m_rs232->cts_handler().set(m_mfp, FUNC(mc68901_device::i2_w));
 	m_rs232->ri_handler().set(m_mfp, FUNC(mc68901_device::i6_w));
diff --git a/src/mame/drivers/harriet.cpp b/src/mame/drivers/harriet.cpp
index 9dac9ad279e..91dbdcd32fa 100644
--- a/src/mame/drivers/harriet.cpp
+++ b/src/mame/drivers/harriet.cpp
@@ -82,6 +82,17 @@ void harriet_state::machine_reset()
 }
 
 
+static const input_device_default terminal_defaults[] =
+{
+	DEVICE_INPUT_DEFAULTS( "RS232_RXBAUD", 0xff, RS232_BAUD_19200 )
+	DEVICE_INPUT_DEFAULTS( "RS232_TXBAUD", 0xff, RS232_BAUD_19200 )
+	DEVICE_INPUT_DEFAULTS( "RS232_STARTBITS", 0xff, RS232_STARTBITS_1 )
+	DEVICE_INPUT_DEFAULTS( "RS232_DATABITS", 0xff, RS232_DATABITS_8 )
+	DEVICE_INPUT_DEFAULTS( "RS232_PARITY", 0xff, RS232_PARITY_NONE )
+	DEVICE_INPUT_DEFAULTS( "RS232_STOPBITS", 0xff, RS232_STOPBITS_1 )
+	{ nullptr, 0, 0 }
+};
+
 void harriet_state::harriet(machine_config &config)
 {
 	M68010(config, m_maincpu, 40_MHz_XTAL / 4); // MC68010FN10
@@ -91,11 +102,9 @@ void harriet_state::harriet(machine_config &config)
 
 	mc68901_device &mfp(MC68901(config, "mfp", 40_MHz_XTAL / 16));
 	mfp.set_timer_clock(2.4576_MHz_XTAL);
-	mfp.set_rx_clock(9600);
-	mfp.set_tx_clock(9600);
 	mfp.out_so_cb().set("rs232", FUNC(rs232_port_device::write_txd));
-	//mfp.out_tco_cb().set("mfp", FUNC(mc68901_device::rc_w));
-	//mfp.out_tdo_cb().set("mfp", FUNC(mc68901_device::tc_w));
+	mfp.out_tco_cb().set("mfp", FUNC(mc68901_device::rc_w));
+	mfp.out_tdo_cb().set("mfp", FUNC(mc68901_device::tc_w));
 
 	HD63450(config, "dmac", 40_MHz_XTAL / 4, "maincpu"); // MC68450R10 (or HD68450Y-10)
 
@@ -103,8 +112,9 @@ void harriet_state::harriet(machine_config &config)
 	NVRAM(config, "zpram", nvram_device::DEFAULT_ALL_0); // MK48Z02
 
 	rs232_port_device &rs232(RS232_PORT(config, "rs232", default_rs232_devices, "terminal"));
-	rs232.rxd_handler().set("mfp", FUNC(mc68901_device::write_rx));
+	rs232.rxd_handler().set("mfp", FUNC(mc68901_device::si_w));
 	rs232.rxd_handler().append("mfp", FUNC(mc68901_device::tbi_w));
+	rs232.set_option_device_input_defaults("terminal", terminal_defaults);
 
 	NSCSI_BUS(config, "scsia");
 	NSCSI_CONNECTOR(config, "scsia:7").option_set("wdc", WD33C93A).clock(40_MHz_XTAL / 4);
diff --git a/src/mame/drivers/indiana.cpp b/src/mame/drivers/indiana.cpp
index 9e87da7198b..3466fb936c1 100644
--- a/src/mame/drivers/indiana.cpp
+++ b/src/mame/drivers/indiana.cpp
@@ -1,5 +1,5 @@
 // license:BSD-3-Clause
-// copyright-holders:Miodrag Milanovic
+// copyright-holders:Miodrag Milanovic, AJR
 /***************************************************************************
 
         Indiana University 68030 board
@@ -15,7 +15,8 @@
 ****************************************************************************/
 
 #include "emu.h"
-#include "bus/rs232/keyboard.h"
+#include "bus/pc_kbd/keyboards.h"
+#include "bus/pc_kbd/pc_kbdc.h"
 #include "cpu/m68000/m68000.h"
 #include "bus/isa/com.h"
 #include "bus/isa/fdc.h"
@@ -24,17 +25,19 @@
 #include "bus/isa/isa_cards.h"
 #include "bus/isa/vga.h"
 #include "machine/mc68901.h"
+#include "sound/spkrdev.h"
+#include "speaker.h"
 
-#define M68K_TAG "maincpu"
 #define ISABUS_TAG "isa"
-#define MFP_TAG "mfp"
 
 class indiana_state : public driver_device
 {
 public:
 	indiana_state(const machine_config &mconfig, device_type type, const char *tag)
 		: driver_device(mconfig, type, tag) ,
-		m_maincpu(*this, M68K_TAG) { }
+		m_maincpu(*this, "maincpu")
+	{
+	}
 
 	void indiana(machine_config &config);
 
@@ -52,7 +55,7 @@ void indiana_state::indiana_mem(address_map &map)
 	map.unmap_value_high();
 	map(0x00000000, 0x0000ffff).mirror(0x7f800000).rom().region("user1", 0); // 64Kb of EPROM
 	map(0x00100000, 0x00107fff).mirror(0x7f8f8000).ram(); // SRAM 32Kb of SRAM
-	map(0x00200000, 0x002fffff).rw(MFP_TAG, FUNC(mc68901_device::read), FUNC(mc68901_device::write)).mirror(0x7f800000); // MFP
+	map(0x00200000, 0x002fffff).rw("mfp", FUNC(mc68901_device::read), FUNC(mc68901_device::write)).mirror(0x7f800000); // MFP
 	map(0x00400000, 0x004fffff).rw(ISABUS_TAG, FUNC(isa16_device::io16_swap_r), FUNC(isa16_device::io16_swap_w)).mirror(0x7f800000); // 16 bit PC IO
 	map(0x00500000, 0x005fffff).rw(ISABUS_TAG, FUNC(isa16_device::mem16_swap_r), FUNC(isa16_device::mem16_swap_w)).mirror(0x7f800000); // 16 bit PC MEM
 	map(0x00600000, 0x006fffff).rw(ISABUS_TAG, FUNC(isa16_device::io_r), FUNC(isa16_device::io_w)).mirror(0x7f800000); // 8 bit PC IO
@@ -86,38 +89,46 @@ void indiana_isa_cards(device_slot_interface &device)
 	device.option_add("ide", ISA16_IDE);
 }
 
-static DEVICE_INPUT_DEFAULTS_START( keyboard )
-	DEVICE_INPUT_DEFAULTS( "RS232_TXBAUD", 0xff, RS232_BAUD_1200 )
-	DEVICE_INPUT_DEFAULTS( "RS232_STARTBITS", 0xff, RS232_STARTBITS_1 )
-	DEVICE_INPUT_DEFAULTS( "RS232_DATABITS", 0xff, RS232_DATABITS_8 )
-	DEVICE_INPUT_DEFAULTS( "RS232_PARITY", 0xff, RS232_PARITY_NONE )
-	DEVICE_INPUT_DEFAULTS( "RS232_STOPBITS", 0xff, RS232_STOPBITS_1 )
-DEVICE_INPUT_DEFAULTS_END
-
 void indiana_state::indiana(machine_config &config)
 {
 	/* basic machine hardware */
-	M68030(config, m_maincpu, XTAL(16'000'000));
+	M68030(config, m_maincpu, 16_MHz_XTAL);
 	m_maincpu->set_addrmap(AS_PROGRAM, &indiana_state::indiana_mem);
 
-	// FIXME: determine ISA bus clock
-	isa16_device &isa(ISA16(config, ISABUS_TAG, 0));
+	isa16_device &isa(ISA16(config, ISABUS_TAG, 16_MHz_XTAL / 2)); // OSC = CLK = CLK8
 	isa.set_custom_spaces();
+	isa.irq3_callback().set_inputline(m_maincpu, M68K_IRQ_5);
+	isa.irq4_callback().set_inputline(m_maincpu, M68K_IRQ_4);
+	isa.irq5_callback().set_inputline(m_maincpu, M68K_IRQ_3);
+	isa.irq6_callback().set_inputline(m_maincpu, M68K_IRQ_2);
+	isa.irq7_callback().set_inputline(m_maincpu, M68K_IRQ_1);
+	isa.irq2_callback().set("mfp", FUNC(mc68901_device::i7_w)); // IRQ9
+	isa.irq10_callback().set("mfp", FUNC(mc68901_device::i6_w));
+	isa.irq11_callback().set("mfp", FUNC(mc68901_device::i5_w));
+	isa.irq12_callback().set("mfp", FUNC(mc68901_device::i4_w));
+	isa.irq14_callback().set("mfp", FUNC(mc68901_device::i3_w));
+	isa.irq15_callback().set("mfp", FUNC(mc68901_device::i2_w));
 
 	ISA16_SLOT(config, "isa1", 0, ISABUS_TAG, indiana_isa_cards, "vga", false);
 	ISA16_SLOT(config, "isa2", 0, ISABUS_TAG, indiana_isa_cards, "fdc_at", false);
 	ISA16_SLOT(config, "isa3", 0, ISABUS_TAG, indiana_isa_cards, "comat", false);
 	ISA16_SLOT(config, "isa4", 0, ISABUS_TAG, indiana_isa_cards, "ide", false);
 
-	mc68901_device &mfp(MC68901(config, MFP_TAG, XTAL(16'000'000)/4));
-	mfp.set_timer_clock(XTAL(16'000'000)/4);
-	mfp.set_rx_clock(0);
-	mfp.set_tx_clock(0);
-	mfp.out_so_cb().set("keyboard", FUNC(rs232_port_device::write_txd));
+	pc_kbdc_device &pc_kbdc(PC_KBDC(config, "pc_kbdc", 0));
+	pc_kbdc.out_data_cb().set("mfp", FUNC(mc68901_device::i0_w));
+	pc_kbdc.out_data_cb().append("mfp", FUNC(mc68901_device::si_w));
+	pc_kbdc.out_clock_cb().set("mfp", FUNC(mc68901_device::i1_w));
+	pc_kbdc.out_clock_cb().append("mfp", FUNC(mc68901_device::rc_w));
 
-	rs232_port_device &keyboard(RS232_PORT(config, "keyboard", default_rs232_devices, "keyboard"));
-	keyboard.rxd_handler().set(MFP_TAG, FUNC(mc68901_device::write_rx));
-	keyboard.set_option_device_input_defaults("keyboard", DEVICE_INPUT_DEFAULTS_NAME(keyboard));
+	PC_KBDC_SLOT(config, "kbd", pc_at_keyboards, STR_KBD_IBM_PC_AT_84).set_pc_kbdc_slot(subdevice("pc_kbdc"));
+
+	mc68901_device &mfp(MC68901(config, "mfp", 16_MHz_XTAL / 4));
+	mfp.set_timer_clock(16_MHz_XTAL / 16);
+	mfp.out_irq_cb().set_inputline(m_maincpu, M68K_IRQ_6);
+	mfp.out_tdo_cb().set("speaker", FUNC(speaker_sound_device::level_w));
+
+	SPEAKER(config, "mono").front_center();
+	SPEAKER_SOUND(config, "speaker").add_route(ALL_OUTPUTS, "mono", 0.50);
 }
 
 /* ROM definition */
diff --git a/src/mame/drivers/micro3d.cpp b/src/mame/drivers/micro3d.cpp
index 9ffdcd847d7..d55a9a0ad94 100644
--- a/src/mame/drivers/micro3d.cpp
+++ b/src/mame/drivers/micro3d.cpp
@@ -346,11 +346,9 @@ void micro3d_state::micro3d(machine_config &config)
 
 	mc68901_device &mfp(MC68901(config, "mfp", 4000000));
 	mfp.set_timer_clock(4000000);
-	mfp.set_rx_clock(0);
-	mfp.set_tx_clock(0);
 	mfp.out_irq_cb().set_inputline("maincpu", M68K_IRQ_4);
-	//mfp.out_tao_cb().set("mfp", FUNC(mc68901_device::rc_w));
-	//mfp.out_tao_cb().append("mfp", FUNC(mc68901_device::tc_w));
+	mfp.out_tao_cb().set("mfp", FUNC(mc68901_device::rc_w));
+	mfp.out_tao_cb().append("mfp", FUNC(mc68901_device::tc_w));
 	mfp.out_tco_cb().set("mfp", FUNC(mc68901_device::tbi_w));
 
 	NVRAM(config, "nvram", nvram_device::DEFAULT_ALL_0);
diff --git a/src/mame/drivers/tti.cpp b/src/mame/drivers/tti.cpp
index 16b1f5b8815..82eb421f8e0 100644
--- a/src/mame/drivers/tti.cpp
+++ b/src/mame/drivers/tti.cpp
@@ -157,9 +157,9 @@ void tti_state::tti(machine_config &config)
 	m_maincpu->set_addrmap(m68008_device::AS_CPU_SPACE, &tti_state::fc7_map);
 
 	MC68901(config, m_mfp, 20_MHz_XTAL / 2); // guess
-	m_mfp->set_timer_clock(20_MHz_XTAL / 2); // guess
-	m_mfp->set_rx_clock(9600); // for testing (FIXME: actually 16x)
-	m_mfp->set_tx_clock(9600); // for testing (FIXME: actually 16x)
+	m_mfp->set_timer_clock(2'457'600); // guess
+	m_mfp->out_tco_cb().set(m_mfp, FUNC(mc68901_device::rc_w));
+	m_mfp->out_tdo_cb().set(m_mfp, FUNC(mc68901_device::tc_w));
 	m_mfp->out_so_cb().set("rs232", FUNC(rs232_port_device::write_txd));
 	m_mfp->out_irq_cb().set_inputline("maincpu", M68K_IRQ_2); // probably
 
@@ -174,7 +174,7 @@ void tti_state::tti(machine_config &config)
 	NSCSI_CONNECTOR(config, "scsibus:7", tti_scsi_devices, "asc", true).set_option_machine_config("asc", [this] (device_t *device) { asc_config(device); });
 
 	rs232_port_device &rs232(RS232_PORT(config, "rs232", default_rs232_devices, "terminal"));
-	rs232.rxd_handler().set(m_mfp, FUNC(mc68901_device::write_rx));
+	rs232.rxd_handler().set(m_mfp, FUNC(mc68901_device::si_w));
 
 	EEPROM_X24C44_16BIT(config, "novram").do_callback().set("mfp", FUNC(mc68901_device::i0_w));
 
diff --git a/src/mame/drivers/x68k.cpp b/src/mame/drivers/x68k.cpp
index 3d190dc1d5a..4737c7fc512 100644
--- a/src/mame/drivers/x68k.cpp
+++ b/src/mame/drivers/x68k.cpp
@@ -1630,14 +1630,13 @@ void x68k_state::x68000_base(machine_config &config)
 	/* device hardware */
 	MC68901(config, m_mfpdev, 16_MHz_XTAL / 4);
 	m_mfpdev->set_timer_clock(16_MHz_XTAL / 4);
-	m_mfpdev->set_rx_clock(0);
-	m_mfpdev->set_tx_clock(0);
 	m_mfpdev->out_irq_cb().set(FUNC(x68k_state::mfp_irq_callback));
-	m_mfpdev->out_tbo_cb().set(m_mfpdev, FUNC(mc68901_device::clock_w));
+	m_mfpdev->out_tbo_cb().set(m_mfpdev, FUNC(mc68901_device::tc_w));
+	m_mfpdev->out_tbo_cb().append(m_mfpdev, FUNC(mc68901_device::rc_w));
 	m_mfpdev->out_so_cb().set("keyboard", FUNC(rs232_port_device::write_txd));
 
 	rs232_port_device &keyboard(RS232_PORT(config, "keyboard", keyboard_devices, "x68k"));
-	keyboard.rxd_handler().set(m_mfpdev, FUNC(mc68901_device::write_rx));
+	keyboard.rxd_handler().set(m_mfpdev, FUNC(mc68901_device::si_w));
 
 	I8255A(config, m_ppi, 0);
 	m_ppi->in_pa_callback().set(FUNC(x68k_state::ppi_port_a_r));
diff --git a/src/mame/includes/atarist.h b/src/mame/includes/atarist.h
index 2c4d97fac46..cc369d40452 100644
--- a/src/mame/includes/atarist.h
+++ b/src/mame/includes/atarist.h
@@ -238,9 +238,6 @@ public:
 
 	DECLARE_WRITE_LINE_MEMBER( ikbd_tx_w );
 
-	DECLARE_READ8_MEMBER( mfp_gpio_r );
-	DECLARE_WRITE_LINE_MEMBER( mfp_tdo_w );
-
 	DECLARE_WRITE_LINE_MEMBER( write_acia_clock );
 
 	void toggle_dma_fifo();
diff --git a/src/mame/machine/x68k_kbd.cpp b/src/mame/machine/x68k_kbd.cpp
index 6704afad127..d74a77f17a6 100644
--- a/src/mame/machine/x68k_kbd.cpp
+++ b/src/mame/machine/x68k_kbd.cpp
@@ -276,7 +276,7 @@ void x68k_keyboard_device::device_reset()
 	buffered_rs232_device::device_reset();
 
 	set_data_frame(1, 8, PARITY_NONE, STOP_BITS_1);
-	set_rate(38'400); // TODO: Should be 2400 but MC68901 doesn't support divide by 16
+	set_rate(2400);
 	receive_register_reset();
 	transmit_register_reset();