SCC/SCC+ device interface

#include <scc.h> Inspect, discover, enable/disable to access registers, of the SCC/SCC+ sound chip. More...

Collaboration diagram for SCC/SCC+ device interface:

Data Structures
struct	SCC_Waveform
	The structure of the SCC/SCC+ 32-byte waveform data register. More...
struct	SCC_Channel
	Device interface for a sound channel of SCC/SCC+ sound chip. More...
struct	SCC_Device
	Device interface for SCC/SCC+ sound chip. More...
struct	SCC
	SCC Handle. More...

Functions
uint8_t	SCC_inspect (uint8_t slot)
	MSX Inspect whether SCC/SCC+ is on the given slot.
uint8_t	SCC_find (struct SCC *scc)
	MSX Find SCC/SCC+ sound chip.
void	SCC_set_mode (struct SCC *scc, uint8_t mode)
	MSX Set the SCC handle to SCC compatible mode or SCC+ mode.
uint8_t	SCC_get_mode (struct SCC *scc)
	MSX Check which mode the SCC handle is set to.
void	SCC_enable (const struct SCC *scc)
	MSX Enable SCC/SCC+ sound chip.
void	SCC_disable (const struct SCC *scc)
	MSX Disable SCC/SCC+ sound chip.

Detailed Description

#include <scc.h> Inspect, discover, enable/disable to access registers, of the SCC/SCC+ sound chip.

Example
The following code detects the Konami SCC/SCC+ sound chip and plays a triangular wave test tone if detected.

// -*- coding: utf-8-unix -*-
/*
 * Copyright (c) 2021-2024 Daishi Mori (mori0091)
 *
 * This software is released under the MIT License.\n
 * See https://github.com/mori0091/libmsx/blob/main/LICENSE
 *
 * GitHub libmsx project\n
 * https://github.com/mori0091/libmsx
 */
#include <string.h>
 
#include <msx.h>
#include <scc.h>
 
const int8_t triangle[32] = {
  0, 16, 32, 48, 64, 80, 96, 112,
  127, 112, 96, 80, 64, 48, 32, 16,
  0, -16, -32, -48, -64, -80, -96, -112,
  -128, -112, -96, -80, -64, -48, -32, -16,
};
 
static struct SCC scc;
 
void test_SCC(void) {
  if (!scc.slot) return;
  SCC_enable(&scc);
  {
    uint8_t slot_p2 = msx_get_slot((void *)0x8000);
    msx_ENASLT(scc.slot, (void *)0x8000);
    {
      memcpy((void *)scc.device->channels[0].wo_waveform, triangle, 32);
      *scc.device->rw_channel_mask = 0x01; // unmute ch1
      *scc.device->channels[0].rw_volume = 15;
      *scc.device->channels[0].rw_fdr = 0x11d; // O4 G
    }
    msx_ENASLT(slot_p2, (void *)0x8000);
    __asm__("ei");
  }
  SCC_disable(&scc);
}
 
void main(void) {
  if (SCC_find(&scc)) {
    test_SCC();
  }
  for (;;) {
    await_vsync();
  }
}

---

Data Structure Documentation

SCC_Waveform

struct SCC_Waveform

The structure of the SCC/SCC+ 32-byte waveform data register.

Definition at line 50 of file scc.h.

Data Fields
int8_t	data[32]

SCC_Channel

struct SCC_Channel

Device interface for a sound channel of SCC/SCC+ sound chip.

Definition at line 57 of file scc.h.

Collaboration diagram for SCC_Channel:

Data Fields
volatile const struct SCC_Waveform *	ro_waveform	Pointer to read data from the 32-byte waveform data register. Note Read Only.
volatile struct SCC_Waveform *	wo_waveform	Pointer to write data to the 32-byte waveform data register. Note Write Only.
volatile uint16_t *	rw_fdr	Pointer to read/write data from/to the frequency division ratio register.
volatile uint8_t *	rw_volume	Pointer to read/write data from/to the volume register.

SCC_Device

struct SCC_Device

Device interface for SCC/SCC+ sound chip.

Definition at line 81 of file scc.h.

Collaboration diagram for SCC_Device:

Data Fields
volatile uint8_t *	rw_channel_mask	Pointer to read/write a value from/to the channel mask register.
volatile uint8_t *	wo_deformation	Pointer to write a value to the deformation register. Note Write Only.
struct SCC_Channel	channels[5]	Device interface for each 5 channels.

SCC

struct SCC

SCC Handle.

See also

SCC_find()

SCC_set_mode()

SCC_get_mode()

SCC_enable()

SCC_disable()

Definition at line 106 of file scc.h.

Collaboration diagram for SCC:

Data Fields
uint8_t	slot	Slot address of the SCC/SCC+.
uint8_t	version	1 if SCC, 2 or greater value if SCC+.
uint8_t	mode	1 if SCC compatible mode, 2 if SCC+ mode.
const struct SCC_Device *	device	Pointer to device interface.

Function Documentation

SCC_inspect()

uint8_t SCC_inspect

(

uint8_t

slot

)

MSX Inspect whether SCC/SCC+ is on the given slot.

Parameters

slot	a slot address

Returns

0 if neither SCC or SCC+, 1 if SCC, 2 or greater value if SCC+.

SCC_find()

uint8_t SCC_find

(

struct SCC *

scc

)

MSX Find SCC/SCC+ sound chip.

Parameters

scc	[out] pointer to a SCC handle to be initialized.

Returns

the slot address of SCC/SCC+ if found, 0 otherwise.

Postcondition

If no SCC/SCC+ found, 0 is set to scc->slot.

If a SCC/SCC+ found;

• the slot address of SCC/SCC+ is set to scc->slot,
• 1 is set to scc->version if SCC, or
• 2 or greater value is set to scc->version if SCC+.
• the device interface is set to scc->device.
• the handle is set to SCC compatible mode even if SCC+.

See also

SCC_set_mode()

SCC_get_mode()

SCC_enable()

SCC_disable()

SCC_set_mode()

void SCC_set_mode	(	struct SCC *	scc,
		uint8_t	mode
	)

MSX Set the SCC handle to SCC compatible mode or SCC+ mode.

The scc shall point to a SCC handle initialized by SCC_find().

If scc->version is less than 2 (i.e., not SCC+), do nothing.

The mode set by this function shall be applied to the sound chip the next time SCC_enable() is called.

Parameters

scc	pointer to the SCC handle.
mode	1 for SCC mode, 2 for SCC+ mode, others are ignored.

SCC_get_mode()

uint8_t SCC_get_mode

(

struct SCC *

scc

)

MSX Check which mode the SCC handle is set to.

The scc shall point to a SCC handle initialized by SCC_find().

The mode returned by this function (i.e., the mode set to the SCC handle) may not the current mode of the sound chip. The mode set to the SCC handle shall be applied to the sound chip when SCC_enable() is called.

Parameters

scc	pointer to the SCC handle.

Returns

1 if SCC mode, 2 if SCC+ mode, 0 otherwise.

SCC_enable()

void SCC_enable

(

const struct SCC *

scc

)

MSX Enable SCC/SCC+ sound chip.

Expose SCC/SCC+ sound chip on the slot scc->slot and enable to access registers of the sound chip by inter-slot read/write BIOS function.

The scc shall point to a SCC handle initialized by SCC_find().

Parameters

scc	pointer to the SCC handle.

SCC_disable()

void SCC_disable

(

const struct SCC *

scc

)

MSX Disable SCC/SCC+ sound chip.

Unexpose SCC/SCC+ sound chip on the slot scc->slot and disable to access registers of the sound chip.

The scc shall point to a SCC handle initialized by SCC_find().

Parameters

scc	pointer to the SCC handle.