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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 // license:BSD-3-Clause
// copyright-holders:Bryan McPhail // copyright-holders:Bryan McPhail
/*************************************************************************** /*******************************************************************************
Konami 051649 - SCC1 sound as used in Haunted Castle, City Bomber 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 megaROM cartridges for the MSX. This device only emulates the
sound portion, not the memory mapper. 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. does not share waveram with channel 4.
References: References:
@ -23,10 +23,14 @@
- http://bifi.msxnet.org/msxnet/tech/soundcartridge - http://bifi.msxnet.org/msxnet/tech/soundcartridge
TODO: 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 - test register bits 0-4, not used in any software
***************************************************************************/ *******************************************************************************/
#include "emu.h" #include "emu.h"
#include "k051649.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") DEFINE_DEVICE_TYPE(K051649, k051649_device, "k051649", "K051649 SCC1")
//************************************************************************** //******************************************************************************
// LIVE DEVICE // LIVE DEVICE
//************************************************************************** //******************************************************************************
//------------------------------------------------- //-------------------------------------------------
// k051649_device - constructor // 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) void k051649_device::k051649_waveform_w(offs_t offset, u8 data)