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-rw-r--r--src/devices/sound/megd.cpp118
1 files changed, 118 insertions, 0 deletions
diff --git a/src/devices/sound/megd.cpp b/src/devices/sound/megd.cpp
new file mode 100644
index 00000000000..2790a7ca69c
--- /dev/null
+++ b/src/devices/sound/megd.cpp
@@ -0,0 +1,118 @@
+// license:BSD-3-Clause
+// copyright-holders:Olivier Galibert
+
+// Yamaha MEG - Multiple effects generator
+//
+// Audio dsp dedicated to effects generation
+//
+// Disassembler
+
+#include "emu.h"
+#include "megd.h"
+
+meg_disassembler::meg_disassembler(info *inf) : m_info(inf)
+{
+}
+
+u32 meg_disassembler::opcode_alignment() const
+{
+ return 1;
+}
+
+std::string meg_disassembler::gfp(offs_t address) const
+{
+ if(!m_info)
+ return util::string_format("fp%03x", address);
+ s16 fp = m_info->fp_r(address);
+ return util::string_format("%g", fp / 16384.0);
+}
+
+std::string meg_disassembler::goffset(offs_t address) const
+{
+ return m_info ? util::string_format("%x", m_info->offset_r(address)) : util::string_format("of%02x", address);
+}
+
+u32 meg_disassembler::b(u64 opc, u32 start, u32 count)
+{
+ return (opc >> start) & ((1 << count) - 1);
+}
+
+void meg_disassembler::append(std::string &r, std::string e)
+{
+ if(r != "")
+ r += " ; ";
+ r += e;
+}
+
+// 33333333 33333333 22222222 22222222 11111111 11111111 00000000 00000000
+// fedcba98 76543210 fedcba98 76543210 fedcba98 76543210 fedcba98 76543210
+
+// 66665555 55555544 44444444 33333333 33222222 22221111 11111100 00000000
+// 32109876 54321098 76543210 98765432 10987654 32109876 54321098 76543210
+// XLB----- -rrrrrrr r--mmmmm m-MM---- -P-----* -----Arr rrrrrrmm mmmm----
+
+// m = low is read port, high is write port, memory register
+// r = low is read port, high is high port, rotating register
+
+// X = used for lo-fi variation only
+// L = lfo read
+// * = compute mul
+// A = mul input = m or r
+// P = P sent for register write
+// B = register write to mbuf
+// M = memory mode, none/read/write/read+1
+
+offs_t meg_disassembler::disassemble(std::ostream &stream, offs_t pc, const data_buffer &opcodes, const data_buffer &params)
+{
+ u64 opc = opcodes.r64(pc);
+
+ std::string r;
+
+ r = util::string_format("[m%02x]", b(opc, 39, 6));
+
+ if(b(opc, 62, 1))
+ append(r, "lfo");
+
+ if(b(opc, 23, 1))
+ switch(b(opc, 24, 2)) {
+ case 0:
+ if(b(opc, 18, 1))
+ append(r, util::string_format("p += %s*m%02x", gfp(pc), b(opc, 4, 6)));
+ else
+ append(r, util::string_format("p += %s*r%02x", gfp(pc), b(opc, 10, 8)));
+ break;
+ case 1:
+ append(r, util::string_format("p = %s*(r%02x+m%02x)", gfp(pc), b(opc, 10, 8), b(opc, 4, 6)));
+ break;
+ case 2:
+ append(r, util::string_format("p ?= %s*(r%02x+m%02x)", gfp(pc), b(opc, 10, 8), b(opc, 4, 6)));
+ break;
+ case 3:
+ if(b(opc, 18, 1))
+ append(r, util::string_format("p = %s*m%02x", gfp(pc), b(opc, 4, 6)));
+ else
+ append(r, util::string_format("p = %s*r%02x", gfp(pc), b(opc, 10, 8)));
+ break;
+ }
+
+ if(b(opc, 30, 1)) {
+ if(b(opc, 61, 1))
+ append(r, "mb = p");
+ else if(b(opc, 46, 1) == 1)
+ append(r, util::string_format("m%02x = p", b(opc, 39, 6)));
+ else
+ append(r, util::string_format("r%02x = p", b(opc, 47, 8)));
+ }
+
+ u32 memmode = b(opc, 36, 2);
+ if(memmode) {
+ static const char *modes[4] = { nullptr, "w", "r", "rw" };
+
+ append(r, util::string_format("mem_%s %x +%s", modes[memmode], b(opc, 33, 3), goffset(pc/3)));
+ r += util::string_format("-> m%02x", b(opcodes.r64(pc+2), 39, 6));
+ }
+
+ stream << r;
+
+ return 1 | SUPPORTED;
+}