// license:BSD-3-Clause
// copyright-holders:Fabio Priuli, Philip Bennett, hap
/*****************************************************************************
Fujitsu MB87078 6-bit, 4-channel electronic volume controller emulator
An excerpt from the datasheet about the chip functionality:
"A digital signal input controls gain every 0.5 dB step from 0dB to -32dB.
- Gain variable range: 0 dB to -32 dB by 0.5dB or -infinity
- Gain variable range is expanded to connect two channels serially (0 dB to -64 dB)
- Each channel gain can be set respectively
- Test function is provided (to confirm internal data)
- Data is initialized by reset signal (all channels are set to 0dB)
- Logic I/O is TTL comatible"
There are 6 digital data input/output pins and DSEL pin that selects
the group (there are two) of internal registers to be read/written.
Group 0 is 6-bit gain latch
Group 1 is 5-bit control latch (2-bits are channel select and 3-bits are volume control)
Digital I/O Setting:
/TC DSEL D0 D1 D2 D3 D4 D5 I/O MODES (when /TC==H ->write)
H H DSC1 DSC2 EN C0 C32 X Input mode
H L GD0 GD1 GD2 GD3 GD4 GD5 (set)
L H DSC1 DSC2 EN C0 C32 L Output mode
L L GD0 GD1 GD2 GD3 GD4 GD5 (check)
Channel Setting:
DSC2 DSC1 CHANNEL
L L 0
L H 1
H L 2
H H 3
Electrical Volume Setting:
DATA* GAIN
GD5 GD4 GD3 GD2 GD1 GD0 EN C0 C32 (dB)
1 1 1 1 1 1 1 0 0 0
1 1 1 1 1 0 1 0 0 -0.5
1 1 1 1 0 1 1 0 0 -1
1 1 1 1 0 0 1 0 0 -1.5
1 1 1 0 1 1 1 0 0 -2
[..........................................]
0 0 0 0 0 1 1 0 0 -31
0 0 0 0 0 0 1 0 0 -31.5
X X X X X X 1 X 1 -32
X X X X X X 1 1 0 0
X X X X X X 0 X X -infinity
X=don't care
* When reset, DATA is set to 0 dB (code 111111 100)
MB87078 pins and assigned interface variables/functions
/[ 1] D0 /TC [24]
| [ 2] D1 /WR [23]
data_w()| [ 3] D2 /CE [22]
data_r()| [ 4] D3 DSEL [21]-data_w()/data_r() (offset)
(data) | [ 5] D4 /RESET [20]
\[ 6] D5 /PD [19]
[ 7] DGND VDD [18]
[ 8] AGND 1/2 VDD [17]
[ 9] AIN0 AOUT3 [16]
[10] AOUT0 AIN3 [15]
[11] AIN1 AOUT2 [14]
[12] AOUT1 AIN2 [13]
*****************************************************************************/
#include "emu.h"
#include "mb87078.h"
/*****************************************************************************
DEVICE INTERFACE
*****************************************************************************/
DEFINE_DEVICE_TYPE(MB87078, mb87078_device, "mb87078", "MB87078 Volume Controller")
mb87078_device::mb87078_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
device_t(mconfig, MB87078, tag, owner, clock),
m_gain_changed_cb(*this)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void mb87078_device::device_start()
{
m_data = 0;
m_control = 0;
// invalidate gain index
for (int i = 0; i < 4; i++)
m_gain_index[i] = 66;
// output volume table, 0dB to -32dB in steps of -0.5dB
for (int i = 0; i < (64+1); i++)
m_lut_gains[i] = pow(10.0, (-0.5 * i) / 20.0);
m_lut_gains[65] = 0.0; // -infinity
m_lut_gains[66] = m_lut_gains[0];
// register for savestates
save_item(NAME(m_gain_index));
save_item(NAME(m_channel_latch));
save_item(NAME(m_data));
save_item(NAME(m_control));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void mb87078_device::device_reset()
{
// all channels enabled, and set at 0dB
for (int i = 0; i < 4; i++)
m_channel_latch[i] = 0x7f;
gain_recalc();
}
/*****************************************************************************
IMPLEMENTATION
*****************************************************************************/
void mb87078_device::gain_recalc()
{
for (int i = 0; i < 4; i++)
{
int gain_index;
// EN = 0: -infinity dB
if (~m_channel_latch[i] & 0x40)
gain_index = 65;
// C32 = 1: -32dB
else if (m_channel_latch[i] & 0x100)
gain_index = 64;
// C0 = 1: 0dB
else if (m_channel_latch[i] & 0x80)
gain_index = 0;
else
gain_index = ~m_channel_latch[i] & 0x3f;
// callback on change
if (gain_index != m_gain_index[i])
{
m_gain_index[i] = gain_index;
m_gain_changed_cb((offs_t)i, gain_percent_r(i));
}
}
}
void mb87078_device::data_w(offs_t offset, u8 data)
{
if (offset & 1)
m_control = data & 0x1f;
else
{
m_data = data & 0x3f;
// set channel volume gain
m_channel_latch[m_control & 3] = (m_control << 4 & 0x1c0) | m_data;
gain_recalc();
}
}
u8 mb87078_device::data_r(offs_t offset)
{
return (offset & 1) ? m_control : m_data;
}