i8212: Device overhaul (nw)

- Change the mode setting from a line write to an input callback. This is based on the observation that MD is nearly always tied to either Vcc or GND on actual hardware.
- Make the mode a scoped enumeration.
- Add strobed write handler for input mode. This allows the device to be hooked up in supstarf in place of generic_latch_8_device.
- Add interrupt acknowledge callback for future use.
- Add extensive introductory comments.

src/devices/machine/i8212.cpp

@@ -1,8 +1,40 @@
 // license:BSD-3-Clause
-// copyright-holders:Curt Coder
+// copyright-holders:Curt Coder,AJR
 /**********************************************************************
 
-    Intel 8212 8-Bit Input/Output Port emulation
+    Intel 8212/3212 8-Bit Input/Output Port (Multi-Mode Latch Buffer)
+
+    The Intel 8212 was one of the first in a line of bipolar Schottky
+    peripherals released early on for the 8080. Many of these were
+    assigned alternate part numbers in the 3200 series to identify
+    them with Intel's 3001/3002 bipolar bit-slice processing elements.
+
+    The 8212's MD pin is typically tied to either GND or Vcc to fix
+    the chip in one of its two operating modes. In the input mode
+    (MD = L), data is latched on the falling edge of STB, and the
+    three-state outputs are enabled by a combination of two chip
+    select inputs of opposite polarities. In the output mode (MD = H),
+    data is latched on the falling edge of chip selection, and outputs
+    are always enabled. The service request flip-flop is clocked on
+    the falling edge of STB to produce the INT output, and is reset by
+    either chip selection or the active-low CLR input, the latter
+    also resetting the latched data to zero.
+
+    The 8212 in output mode was often used with the 8080 to latch the
+    status word and with the 8085 to latch the lower address bits.
+
+    RCA's CDP1852 is an almost pin-for-pin CMOS counterpart to the
+    8212. The control lines of the CDP1852, however, work slightly
+    differently, especially in output mode.
+
+    When TI second-sourced the 8080A, they cloned the 8212 as the
+    SN74S412 (and numbered their versions of the 8224, 8228 and 8338
+    similarly). While simpler octal latches from the 7400 series such
+    as 74LS273, 74LS373 and 74LS374 became far more common and widely
+    used, even when a separate service request flip-flop needed to be
+    coupled, the Fairchild Advanced Schottky TTL (FAST) evolution of
+    the 7400 series had both inverting (74F432) and non-inverting
+    (74F412) versions of this device.
 
 **********************************************************************/
 
@@ -19,7 +51,7 @@
 //**************************************************************************
 
 // device type definition
-DEFINE_DEVICE_TYPE(I8212, i8212_device, "i8212", "Intel 8212 I/O")
+DEFINE_DEVICE_TYPE(I8212, i8212_device, "i8212", "Intel 8212 I/O Port")
 
 //-------------------------------------------------
 //  i8212_device - constructor
@@ -30,8 +62,8 @@ i8212_device::i8212_device(const machine_config &mconfig, const char *tag, devic
 	m_write_int(*this),
 	m_read_di(*this),
 	m_write_do(*this),
-	m_md(MODE_INPUT),
+	m_read_md(*this),
-	m_stb(0), m_data(0)
+	m_stb(1), m_data(0)
 {
 }
 
@@ -46,23 +78,37 @@ void i8212_device::device_start()
 	m_write_int.resolve_safe();
 	m_read_di.resolve_safe(0);
 	m_write_do.resolve_safe();
+	m_read_md.resolve_safe(0);
 
 	// register for state saving
-	save_item(NAME(m_md));
 	save_item(NAME(m_stb));
 	save_item(NAME(m_data));
 }
 
 
+//-------------------------------------------------
+//  get_mode - resolve device mode
+//-------------------------------------------------
+
+i8212_device::mode i8212_device::get_mode()
+{
+	return m_read_md() ? mode::OUTPUT : mode::INPUT;
+}
+
+
 //-------------------------------------------------
 //  device_reset - device-specific reset
 //-------------------------------------------------
 
 void i8212_device::device_reset()
 {
+	// clear interrupt line
+	m_write_int(CLEAR_LINE);
+
+	// clear latched data
 	m_data = 0;
 
-	if (m_md == MODE_OUTPUT)
+	if (get_mode() == mode::OUTPUT)
 	{
 		// output data
 		m_write_do((offs_t)0, m_data);
@@ -74,13 +120,28 @@ void i8212_device::device_reset()
 //  read - data latch read
 //-------------------------------------------------
 
-READ8_MEMBER( i8212_device::read )
+READ8_MEMBER(i8212_device::read)
+{
+	if (!machine().side_effect_disabled())
+	{
+		// clear interrupt line
+		m_write_int(CLEAR_LINE);
+	}
+
+	return m_data;
+}
+
+
+//-------------------------------------------------
+//  inta_cb - data latch read (INTA triggered)
+//-------------------------------------------------
+
+IRQ_CALLBACK_MEMBER(i8212_device::inta_cb)
 {
 	// clear interrupt line
 	m_write_int(CLEAR_LINE);
 
-	LOG("I8212 INT: %u\n", CLEAR_LINE);
+	// read latched data as interrupt vector
-
 	return m_data;
 }
 
@@ -89,25 +150,37 @@ READ8_MEMBER( i8212_device::read )
 //  write - data latch write
 //-------------------------------------------------
 
-WRITE8_MEMBER( i8212_device::write )
+WRITE8_MEMBER(i8212_device::write)
 {
+	// clear interrupt line
+	m_write_int(CLEAR_LINE);
+
+	if (get_mode() == mode::OUTPUT)
+	{
 		// latch data
 		m_data = data;
+		LOG("I8212: Writing %02X into latch (output mode)\n", data);
 
 		// output data
 		m_write_do((offs_t)0, m_data);
+	}
 }
 
 
 //-------------------------------------------------
-//  md_w - mode write
+//  strobe - data input strobe
 //-------------------------------------------------
 
-WRITE_LINE_MEMBER( i8212_device::md_w )
+WRITE8_MEMBER(i8212_device::strobe)
 {
-	LOG("I8212 Mode: %s\n", state ? "output" : "input");
+	if (get_mode() == mode::INPUT)
+	{
+		m_data = data;
+		LOG("I8212: Writing %02X into latch (input mode)\n", data);
+	}
 
-	m_md = state;
+	// assert interrupt line
+	m_write_int(ASSERT_LINE);
 }
 
 
@@ -115,22 +188,20 @@ WRITE_LINE_MEMBER( i8212_device::md_w )
 //  stb_w - data strobe write
 //-------------------------------------------------
 
-WRITE_LINE_MEMBER( i8212_device::stb_w )
+WRITE_LINE_MEMBER(i8212_device::stb_w)
 {
-	LOG("I8212 STB: %u\n", state);
+	// active on falling edge
-
-	if (m_md == MODE_INPUT)
-	{
 	if (m_stb && !state)
+	{
+		if (get_mode() == mode::INPUT)
 		{
 			// input data
 			m_data = m_read_di(0);
+			LOG("I8212: Reading %02X into latch (input mode)\n", m_data);
+		}
 
 		// assert interrupt line
 		m_write_int(ASSERT_LINE);
-
-			LOG("I8212 INT: %u\n", ASSERT_LINE);
-		}
 	}
 
 	m_stb = state;

src/devices/machine/i8212.h

@@ -1,8 +1,8 @@
 // license:BSD-3-Clause
-// copyright-holders:Curt Coder
+// copyright-holders:Curt Coder,AJR
 /**********************************************************************
 
-    Intel 8212 8-Bit Input/Output Port emulation
+    Intel 8212/3212 8-Bit Input/Output Port (Multi-Mode Latch Buffer)
 
 **********************************************************************
                             _____   _____
@@ -12,7 +12,7 @@
                    DO1   4 |             | 21  DO8
                    DI2   5 |             | 20  DI7
                    DO2   6 |    8212     | 19  DO7
-                   DI3   7 |             | 18  DI6
+                   DI3   7 |    3212     | 18  DI6
                    DO3   8 |             | 17  DO6
                    DI4   9 |             | 16  DI5
                    DO4  10 |             | 15  DO5
@@ -42,6 +42,9 @@
 #define MCFG_I8212_DO_CALLBACK(_write) \
 	devcb = &i8212_device::set_do_wr_callback(*device, DEVCB_##_write);
 
+#define MCFG_I8212_MD_CALLBACK(_read) \
+	devcb = &i8212_device::set_md_rd_callback(*device, DEVCB_##_read);
+
 
 
 ///*************************************************************************
@@ -52,6 +55,12 @@
 
 class i8212_device : public device_t
 {
+	enum class mode : u8
+	{
+		INPUT,
+		OUTPUT
+	};
+
 public:
 	// construction/destruction
 	i8212_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
@@ -59,12 +68,19 @@ public:
 	template <class Object> static devcb_base &set_int_wr_callback(device_t &device, Object &&cb) { return downcast<i8212_device &>(device).m_write_int.set_callback(std::forward<Object>(cb)); }
 	template <class Object> static devcb_base &set_di_rd_callback(device_t &device, Object &&cb) { return downcast<i8212_device &>(device).m_read_di.set_callback(std::forward<Object>(cb)); }
 	template <class Object> static devcb_base &set_do_wr_callback(device_t &device, Object &&cb) { return downcast<i8212_device &>(device).m_write_do.set_callback(std::forward<Object>(cb)); }
+	template <class Object> static devcb_base &set_md_rd_callback(device_t &device, Object &&cb) { return downcast<i8212_device &>(device).m_read_md.set_callback(std::forward<Object>(cb)); }
 
-	DECLARE_READ8_MEMBER( read );
+	// data read handlers
-	DECLARE_WRITE8_MEMBER( write );
+	DECLARE_READ8_MEMBER(read);
+	IRQ_CALLBACK_MEMBER(inta_cb);
 
-	DECLARE_WRITE_LINE_MEMBER( md_w );
+	// data write handlers
-	DECLARE_WRITE_LINE_MEMBER( stb_w );
+	DECLARE_WRITE8_MEMBER(write);
+	DECLARE_WRITE8_MEMBER(strobe);
+
+	// line write handlers
+	DECLARE_WRITE_LINE_MEMBER(md_w);
+	DECLARE_WRITE_LINE_MEMBER(stb_w);
 
 protected:
 	// device-level overrides
@@ -72,17 +88,14 @@ protected:
 	virtual void device_reset() override;
 
 private:
-	enum
+	// helpers
-	{
+	mode get_mode();
-		MODE_INPUT = 0,
-		MODE_OUTPUT
-	};
 
 	devcb_write_line   m_write_int;
 	devcb_read8        m_read_di;
 	devcb_write8       m_write_do;
+	devcb_read_line    m_read_md;
 
-	int m_md;                   // mode
 	int m_stb;                  // strobe
 	uint8_t m_data;             // data latch
 };

src/mame/drivers/supstarf.cpp

@@ -11,7 +11,7 @@
 #include "emu.h"
 #include "cpu/i8085/i8085.h"
 #include "cpu/mcs48/mcs48.h"
-#include "machine/gen_latch.h"
+#include "machine/i8212.h"
 #include "sound/ay8910.h"
 #include "speaker.h"
 
@@ -45,7 +45,7 @@ private:
 	required_device<cpu_device> m_maincpu;
 	required_device<cpu_device> m_soundcpu;
 	required_device_array<ay8910_device, 2> m_psg;
-	required_device_array<generic_latch_8_device, 2> m_soundlatch;
+	required_device_array<i8212_device, 2> m_soundlatch;
 
 	u8 m_port1_data;
 	bool m_pcs[2];
@@ -54,7 +54,7 @@ private:
 
 static ADDRESS_MAP_START(main_map, AS_PROGRAM, 8, supstarf_state)
 	AM_RANGE(0x0000, 0x3fff) AM_ROM
-	AM_RANGE(0x8000, 0x8000) AM_DEVREAD("soundlatch1", generic_latch_8_device, read) AM_DEVWRITE("soundlatch2", generic_latch_8_device, write)
+	AM_RANGE(0x8000, 0x8000) AM_DEVREAD("soundlatch1", i8212_device, read) AM_DEVWRITE("soundlatch2", i8212_device, strobe)
 	AM_RANGE(0xc000, 0xc7ff) AM_RAM // 5517 (2Kx8) at IC11
 ADDRESS_MAP_END
 
@@ -102,7 +102,7 @@ WRITE8_MEMBER(supstarf_state::psg_latch_w)
 	}
 
 	if (m_latch_select)
-		m_soundlatch[0]->write(space, 0, data);
+		m_soundlatch[0]->strobe(space, 0, data);
 }
 
 WRITE8_MEMBER(supstarf_state::port1_w)
@@ -177,11 +177,13 @@ static MACHINE_CONFIG_START(supstarf)
 	MCFG_MCS48_PORT_P2_OUT_CB(WRITE8(supstarf_state, port2_w))
 	MCFG_MCS48_PORT_T1_IN_CB(READLINE(supstarf_state, phase_detect_r))
 
-	MCFG_GENERIC_LATCH_8_ADD("soundlatch1")
+	MCFG_DEVICE_ADD("soundlatch1", I8212, 0)
-	MCFG_GENERIC_LATCH_DATA_PENDING_CB(INPUTLINE("maincpu", I8085_RST55_LINE))
+	MCFG_I8212_MD_CALLBACK(GND)
+	MCFG_I8212_INT_CALLBACK(INPUTLINE("maincpu", I8085_RST55_LINE))
 
-	MCFG_GENERIC_LATCH_8_ADD("soundlatch2")
+	MCFG_DEVICE_ADD("soundlatch2", I8212, 0)
-	MCFG_GENERIC_LATCH_DATA_PENDING_CB(INPUTLINE("soundcpu", MCS48_INPUT_IRQ))
+	MCFG_I8212_MD_CALLBACK(GND)
+	MCFG_I8212_INT_CALLBACK(INPUTLINE("soundcpu", MCS48_INPUT_IRQ))
 	//MCFG_DEVCB_CHAIN_OUTPUT(INPUTLINE("maincpu", I8085_READY_LINE))
 
 	MCFG_SPEAKER_STANDARD_MONO("mono")