leave specnext_dma as is

src/devices/machine/z80dma.cpp

@@ -896,59 +896,3 @@ ua858d_device::ua858d_device(const machine_config &mconfig, const char *tag, dev
 	: z80dma_device(mconfig, UA858D, tag, owner, clock, dma_mode::UA858D)
 {
 }
-
-
-DEFINE_DEVICE_TYPE(SPECNEXT_DMA, specnext_dma_device, "specnext_dma", "Spectrum Next DMA")
-
-specnext_dma_device::specnext_dma_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
-	: z80dma_device(mconfig, SPECNEXT_DMA, tag, owner, clock, dma_mode::SPEC_NEXT)
-{
-}
-
-void specnext_dma_device::do_write()
-{
-	if (m_dma_mode != dma_mode::SPEC_NEXT)
-	{
-		z80dma_device::do_write();
-	}
-	else
-	{
-		if (m_byte_counter)
-			m_addressB += PORTB_FIXED ? 0 : PORTB_INC ? 1 : -1;
-
-		switch (TRANSFER_MODE)
-		{
-		case TM_TRANSFER:
-			do_transfer_write();
-			break;
-
-		case TM_SEARCH:
-			do_search();
-			break;
-
-		case TM_SEARCH_TRANSFER:
-			do_transfer_write();
-			do_search();
-			break;
-
-		default:
-			logerror("z80dma_do_operation: invalid mode %d!\n", TRANSFER_MODE);
-			break;
-		}
-
-		m_addressA += PORTA_FIXED ? 0 : PORTA_INC ? 1 : -1;
-
-		m_byte_counter++;
-		if ((m_byte_counter + 1) == m_count)
-			m_byte_counter++;
-	}
-}
-
-void specnext_dma_device::write(u8 data)
-{
-	if (m_dma_mode == dma_mode::SPEC_NEXT && data == COMMAND_ENABLE_DMA && num_follow() == 0)
-	{
-		m_byte_counter = 0;
-	}
-	z80dma_device::write(data);
-}

src/devices/machine/z80dma.h

@@ -51,8 +51,7 @@ public:
 	enum class dma_mode : u8
 	{
 		ZILOG = 0,
-		UA858D = 1,
-		SPEC_NEXT = 2
+		UA858D = 1
 	};
 
 	// construction/destruction
@@ -179,20 +178,8 @@ public:
 	ua858d_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
 };
 
-class specnext_dma_device : public z80dma_device
-{
-public:
-	specnext_dma_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
-
-	virtual void write(u8 data) override;
-
-protected:
-	virtual void do_write() override;
-};
-
 // device type definition
 DECLARE_DEVICE_TYPE(Z80DMA, z80dma_device)
 DECLARE_DEVICE_TYPE(UA858D, ua858d_device)
-DECLARE_DEVICE_TYPE(SPECNEXT_DMA, specnext_dma_device)
 
 #endif // MAME_MACHINE_Z80DMA_H

src/mame/sinclair/specnext.cpp

@@ -25,6 +25,7 @@
 #include "specnext_copper.h"
 #include "specnext_ctc.h"
 #include "specnext_divmmc.h"
+#include "specnext_dma.h"
 #include "specnext_multiface.h"
 #include "specnext_layer2.h"
 #include "specnext_lores.h"
@@ -35,7 +36,6 @@
 #include "cpu/z80/z80n.h"
 #include "machine/i2cmem.h"
 #include "machine/spi_sdcard.h"
-#include "machine/z80dma.h"
 #include "sound/ay8910.h"
 #include "sound/dac.h"
 #include "speaker.h"
@@ -1146,13 +1146,13 @@ void specnext_state::mmu_x2_w(offs_t bank, u8 data)
 
 u8 specnext_state::dma_r(bool dma_mode)
 {
-	m_dma->set_dma_mode(dma_mode ? z80dma_device::dma_mode::ZILOG : z80dma_device::dma_mode::SPEC_NEXT);
+	m_dma->dma_mode_w(dma_mode);
 	return m_dma->read();
 }
 
 void specnext_state::dma_w(bool dma_mode, u8 data)
 {
-	m_dma->set_dma_mode(dma_mode ? z80dma_device::dma_mode::ZILOG : z80dma_device::dma_mode::SPEC_NEXT);
+	m_dma->dma_mode_w(dma_mode);
 	m_dma->write(data);
 }
 
@@ -3035,7 +3035,7 @@ void specnext_state::reset_hard()
 	m_nr_02_hard_reset = 0;
 	m_bootrom_en = 1;
 
-	m_dma->set_dma_mode(z80dma_device::dma_mode::SPEC_NEXT);
+	m_dma->dma_mode_w(0);
 	// nmi_mf = 0;
 	// nmi_divmmc = 0;
 	// nmi_expbus = 0;
@@ -3162,7 +3162,7 @@ void specnext_state::machine_reset()
 	m_port_ff_data = 0;
 	m_divmmc_delayed_check = 0;
 
-	m_dma->set_dma_mode(z80dma_device::dma_mode::SPEC_NEXT);
+	m_dma->dma_mode_w(0);
 	//z80_retn_seen_28_d  = 0;
 	//im2_dma_delay  = 0;
 	m_pulse_int_n  = 1;
@@ -3449,7 +3449,7 @@ void specnext_state::tbblue(machine_config &config)
 	m_maincpu->in_nextreg_cb().set(FUNC(specnext_state::reg_r));
 	m_maincpu->out_retn_seen_cb().set(FUNC(specnext_state::leave_nmi));
 	m_maincpu->nomreq_cb().set_nop();
-	m_maincpu->busack_cb().set(m_dma, FUNC(z80dma_device::bai_w));
+	m_maincpu->busack_cb().set(m_dma, FUNC(specnext_dma_device::bai_w));
 
 	SPECNEXT_CTC(config, m_ctc, 28_MHz_XTAL / 8);
 	m_ctc->intr_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);

src/mame/sinclair/specnext_dma.cpp

@@ -0,0 +1,101 @@
+// license:BSD-3-Clause
+// copyright-holders:Andrei I. Holub
+/**********************************************************************
+    Spectrum Next DMA
+
+    Spectrum Next DMA operates in two mode: z80dma compatible and
+    N-mode with Next specific fixes.
+
+    z80dma mode is implemented there based on intensive testing of
+    the device. Potentially any mismatches not related to N-mode
+    covered here must be moved to the z80dma parent.
+
+**********************************************************************/
+
+#include "emu.h"
+#include "specnext_dma.h"
+
+// device type definition
+DEFINE_DEVICE_TYPE(SPECNEXT_DMA, specnext_dma_device, "specnext_dma", "Spectrum Next DMA")
+
+
+// TODO: this stuff is copy/pasted from machine/z80dma.cpp - ideally it wouldn't need to be
+#define WR0                     REG(0, 0)
+#define WR1                     REG(1, 0)
+#define WR2                     REG(2, 0)
+
+#define PORTA_INC               (WR1 & 0x10)
+#define PORTB_INC               (WR2 & 0x10)
+#define PORTA_FIXED             (((WR1 >> 4) & 0x02) == 0x02)
+#define PORTB_FIXED             (((WR2 >> 4) & 0x02) == 0x02)
+
+#define TRANSFER_MODE           (WR0 & 0x03)
+
+
+specnext_dma_device::specnext_dma_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
+	: z80dma_device(mconfig, SPECNEXT_DMA, tag, owner, clock, dma_mode::ZILOG)
+{
+}
+
+void specnext_dma_device::write(u8 data)
+{
+	if (!m_ndma_mode && data == COMMAND_ENABLE_DMA && num_follow() == 0)
+	{
+		m_byte_counter = 0;
+	}
+	z80dma_device::write(data);
+}
+
+void specnext_dma_device::do_write()
+{
+	if (m_ndma_mode)
+	{
+		z80dma_device::do_write();
+		return;
+	}
+	// else (zxnDMA)
+
+	if (m_byte_counter)
+		m_addressB += PORTB_FIXED ? 0 : PORTB_INC ? 1 : -1;
+
+	switch (TRANSFER_MODE)
+	{
+	case TM_TRANSFER:
+		do_transfer_write();
+		break;
+
+	case TM_SEARCH:
+		do_search();
+		break;
+
+	case TM_SEARCH_TRANSFER:
+		do_transfer_write();
+		do_search();
+		break;
+
+	default:
+		logerror("z80dma_do_operation: invalid mode %d!\n", TRANSFER_MODE);
+		break;
+	}
+
+	m_addressA += PORTA_FIXED ? 0 : PORTA_INC ? 1 : -1;
+
+	m_byte_counter++;
+	if ((m_byte_counter + 1) == m_count)
+		m_byte_counter++;
+}
+
+
+void specnext_dma_device::device_start()
+{
+	z80dma_device::device_start();
+
+	save_item(NAME(m_ndma_mode));
+}
+
+void specnext_dma_device::device_reset()
+{
+	z80dma_device::device_reset();
+
+	m_ndma_mode = 0;
+}

src/mame/sinclair/specnext_dma.h

@@ -0,0 +1,31 @@
+// license:BSD-3-Clause
+// copyright-holders:Andrei I. Holub
+#ifndef MAME_SINCLAIR_SPECNEXT_DMA_H
+#define MAME_SINCLAIR_SPECNEXT_DMA_H
+
+#pragma once
+
+#include "machine/z80dma.h"
+
+class specnext_dma_device : public z80dma_device
+{
+public:
+	specnext_dma_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
+
+	void dma_mode_w(bool dma_mode) { m_ndma_mode = dma_mode; }
+
+	virtual void write(u8 data) override;
+
+protected:
+	virtual void device_start() override ATTR_COLD;
+	virtual void device_reset() override ATTR_COLD;
+
+	virtual void do_write() override;
+
+private:
+	bool m_ndma_mode; // 0 = zxn dma, 1 = z80 dma
+};
+
+DECLARE_DEVICE_TYPE(SPECNEXT_DMA, specnext_dma_device)
+
+#endif // MAME_SINCLAIR_SPECNEXT_DMA_H