From 707d36ab2fbedd6f28019a3bb8587a79e49eb00e Mon Sep 17 00:00:00 2001
From: hap <happppp@users.noreply.github.com>
Date: Thu, 29 Feb 2024 15:02:24 +0100
Subject: okim6258: small cleanup

---
 src/devices/sound/okim6258.cpp | 76 ++++++++++++++++++------------------------
 src/devices/sound/okim6258.h   | 16 ++++-----
 src/devices/sound/okim6588.cpp | 11 ++++--
 src/devices/sound/okim6588.h   |  2 +-
 4 files changed, 48 insertions(+), 57 deletions(-)

diff --git a/src/devices/sound/okim6258.cpp b/src/devices/sound/okim6258.cpp
index 349fe9ca13c..171100e2080 100644
--- a/src/devices/sound/okim6258.cpp
+++ b/src/devices/sound/okim6258.cpp
@@ -2,15 +2,15 @@
 // copyright-holders:Barry Rodewald
 /**********************************************************************************************
  *
- *   OKI MSM6258 ADPCM
+ *   OKI MSM6258 ADPCM Speech Processor
  *
  *   TODO:
- *   3-bit ADPCM support
- *   Recording?
+ *   - 3-bit ADPCM support
+ *   - Use okiadpcm.* helper?
+ *   - Recording?
  *
  **********************************************************************************************/
 
-
 #include "emu.h"
 #include "okim6258.h"
 
@@ -46,19 +46,19 @@ DEFINE_DEVICE_TYPE(OKIM6258, okim6258_device, "okim6258", "OKI MSM6258 ADPCM")
 //  okim6258_device - constructor
 //-------------------------------------------------
 
-okim6258_device::okim6258_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: device_t(mconfig, OKIM6258, tag, owner, clock),
-		device_sound_interface(mconfig, *this),
-		m_status(0),
-		m_start_divider(0),
-		m_divider(512),
-		m_adpcm_type(0),
-		m_data_in(0),
-		m_nibble_shift(0),
-		m_stream(nullptr),
-		m_output_bits(0),
-		m_signal(0),
-		m_step(0)
+okim6258_device::okim6258_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+	device_t(mconfig, OKIM6258, tag, owner, clock),
+	device_sound_interface(mconfig, *this),
+	m_status(0),
+	m_start_divider(0),
+	m_divider(512),
+	m_adpcm_type(0),
+	m_data_in(0),
+	m_nibble_shift(0),
+	m_stream(nullptr),
+	m_output_bits(0),
+	m_signal(0),
+	m_step(0)
 {
 }
 
@@ -93,7 +93,7 @@ static void compute_tables()
 		for (nib = 0; nib < 16; nib++)
 		{
 			diff_lookup[step*16 + nib] = nbl2bit[nib][0] *
-				(stepval   * nbl2bit[nib][1] +
+					(stepval  * nbl2bit[nib][1] +
 					stepval/2 * nbl2bit[nib][2] +
 					stepval/4 * nbl2bit[nib][3] +
 					stepval/8);
@@ -119,7 +119,13 @@ void okim6258_device::device_start()
 	m_signal = -2;
 	m_step = 0;
 
-	state_save_register();
+	// register for savestates
+	save_item(NAME(m_status));
+	save_item(NAME(m_divider));
+	save_item(NAME(m_data_in));
+	save_item(NAME(m_nibble_shift));
+	save_item(NAME(m_signal));
+	save_item(NAME(m_step));
 }
 
 
@@ -171,25 +177,6 @@ void okim6258_device::sound_stream_update(sound_stream &stream, std::vector<read
 	}
 }
 
-
-
-/**********************************************************************************************
-
-     state save support for MAME
-
-***********************************************************************************************/
-
-void okim6258_device::state_save_register()
-{
-	save_item(NAME(m_status));
-	save_item(NAME(m_divider));
-	save_item(NAME(m_data_in));
-	save_item(NAME(m_nibble_shift));
-	save_item(NAME(m_signal));
-	save_item(NAME(m_step));
-}
-
-
 int16_t okim6258_device::clock_adpcm(uint8_t nibble)
 {
 	int32_t max = (1 << (m_output_bits - 1)) - 1;
@@ -217,7 +204,7 @@ int16_t okim6258_device::clock_adpcm(uint8_t nibble)
 
 /**********************************************************************************************
 
-     okim6258::set_divider -- set the master clock divider
+     set_divider -- set the master clock divider
 
 ***********************************************************************************************/
 
@@ -230,7 +217,7 @@ void okim6258_device::set_divider(int val)
 
 /**********************************************************************************************
 
-     okim6258::set_clock -- set the master clock
+     set_clock -- set the master clock
 
 ***********************************************************************************************/
 
@@ -242,7 +229,7 @@ void okim6258_device::device_clock_changed()
 
 /**********************************************************************************************
 
-     okim6258::get_vclk -- get the VCLK/sampling frequency
+     get_vclk -- get the VCLK/sampling frequency
 
 ***********************************************************************************************/
 
@@ -254,7 +241,7 @@ int okim6258_device::get_vclk()
 
 /**********************************************************************************************
 
-     okim6258_status_r -- read the status port of an OKIM6258-compatible chip
+     status_r -- read the status port of an OKIM6258-compatible chip
 
 ***********************************************************************************************/
 
@@ -268,9 +255,10 @@ uint8_t okim6258_device::status_r()
 
 /**********************************************************************************************
 
-     okim6258_data_w -- write to the control port of an OKIM6258-compatible chip
+     data_w -- write to the control port of an OKIM6258-compatible chip
 
 ***********************************************************************************************/
+
 void okim6258_device::data_w(uint8_t data)
 {
 	/* update the stream */
@@ -283,7 +271,7 @@ void okim6258_device::data_w(uint8_t data)
 
 /**********************************************************************************************
 
-     okim6258_ctrl_w -- write to the control port of an OKIM6258-compatible chip
+     ctrl_w -- write to the control port of an OKIM6258-compatible chip
 
 ***********************************************************************************************/
 
diff --git a/src/devices/sound/okim6258.h b/src/devices/sound/okim6258.h
index 95189f0ef3c..e7e4a25c414 100644
--- a/src/devices/sound/okim6258.h
+++ b/src/devices/sound/okim6258.h
@@ -50,20 +50,18 @@ protected:
 	virtual void sound_stream_update(sound_stream &stream, std::vector<read_stream_view> const &inputs, std::vector<write_stream_view> &outputs) override;
 
 private:
-	void state_save_register();
 	int16_t clock_adpcm(uint8_t nibble);
 
 	uint8_t  m_status;
 
 	uint32_t m_start_divider;
-	uint32_t m_divider;         /* master clock divider */
-	uint8_t m_adpcm_type;       /* 3/4 bit ADPCM select */
-	uint8_t m_data_in;          /* ADPCM data-in register */
-	uint8_t m_nibble_shift;     /* nibble select */
-	sound_stream *m_stream;   /* which stream are we playing on? */
-
-	uint8_t m_output_bits;      /* D/A precision is 10-bits but 12-bit data can be
-	                           output serially to an external DAC */
+	uint32_t m_divider;         // master clock divider
+	uint8_t m_adpcm_type;       // 3/4 bit ADPCM select
+	uint8_t m_data_in;          // ADPCM data-in register
+	uint8_t m_nibble_shift;     // nibble select
+	sound_stream *m_stream;     // which stream are we playing on?
+
+	uint8_t m_output_bits;      // D/A precision is 10-bits but 12-bit data can be output serially to an external DAC
 
 	int32_t m_signal;
 	int32_t m_step;
diff --git a/src/devices/sound/okim6588.cpp b/src/devices/sound/okim6588.cpp
index 7704c61d315..4e28ddd1ee3 100644
--- a/src/devices/sound/okim6588.cpp
+++ b/src/devices/sound/okim6588.cpp
@@ -4,6 +4,8 @@
 
 OKI MSM6588 ADPCM Recorder
 
+It has similar functionality to MSM6258.
+
 TODO:
 - it only supports MCU mode EXT playback, nothing else emulated yet
 - status register read (eg. BUSY flag)
@@ -123,10 +125,13 @@ TIMER_CALLBACK_MEMBER(okim6588_device::set_mon)
 	m_write_mon(param ? 1 : 0);
 }
 
-s32 okim6588_device::get_adpcm_sample(u8 data)
+s16 okim6588_device::get_adpcm_sample(u8 data)
 {
-	u8 mask = m_vds_bit ? 0xf : 0xe;
-	return m_adpcm.clock(data & mask);
+	// 4-bit or 3-bit input
+	if (m_vds_bit)
+		return m_adpcm.clock(data & 0xf);
+	else
+		return m_adpcm.clock((data & 0xc) | (data >> 1 & 1));
 }
 
 void okim6588_device::reset_adpcm()
diff --git a/src/devices/sound/okim6588.h b/src/devices/sound/okim6588.h
index 7382902c3d8..28bcec029aa 100644
--- a/src/devices/sound/okim6588.h
+++ b/src/devices/sound/okim6588.h
@@ -78,7 +78,7 @@ private:
 
 	TIMER_CALLBACK_MEMBER(clock_adpcm);
 	TIMER_CALLBACK_MEMBER(set_mon);
-	s32 get_adpcm_sample(u8 data);
+	s16 get_adpcm_sample(u8 data);
 	void reset_adpcm();
 };
 
-- 
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