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k051649: add note about bus conflicts

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hap 2023-07-24 11:46:45 +02:00
parent 1b60d603ec
commit f4ceebf442
1 changed files with 11 additions and 7 deletions
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18
src/devices/sound/k051649.cpp
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@ -1,6 +1,6 @@
// license:BSD-3-Clause
// copyright-holders:Bryan McPhail
/***************************************************************************
/*******************************************************************************
Konami 051649 - SCC1 sound as used in Haunted Castle, City Bomber
@ -15,7 +15,7 @@
megaROM cartridges for the MSX. This device only emulates the
sound portion, not the memory mapper.
K052539 is more or less equivalent to this chip except channel 5
052539 is more or less equivalent to this chip except channel 5
does not share waveram with channel 4.
References:
@ -23,10 +23,14 @@
- http://bifi.msxnet.org/msxnet/tech/soundcartridge
TODO:
- make K052539 a subdevice
- make 052539 a subdevice
- bus conflicts on 051649 (not 052539). When the CPU accesses waveform RAM
and the SCC is reading it at the same time, it can cause audible spikes.
A similar thing happens internally when the shared ch4/ch5 do a read at
the same time.
- test register bits 0-4, not used in any software
***************************************************************************/
*******************************************************************************/
#include "emu.h"
#include "k051649.h"
@ -45,9 +49,9 @@ void k051649_device::scc_map(address_map &map)
DEFINE_DEVICE_TYPE(K051649, k051649_device, "k051649", "K051649 SCC1")
//**************************************************************************
//******************************************************************************
// LIVE DEVICE
//**************************************************************************
//******************************************************************************
//-------------------------------------------------
// k051649_device - constructor
@ -159,7 +163,7 @@ void k051649_device::sound_stream_update(sound_stream &stream, std::vector<read_
}
/********************************************************************************/
/******************************************************************************/
void k051649_device::k051649_waveform_w(offs_t offset, u8 data)