From 05e59cf6aa66da9d707e53ae21971ab75879a94a Mon Sep 17 00:00:00 2001
From: smf- <smf-@users.noreply.github.com>
Date: Sat, 13 Jan 2018 23:03:23 +0000
Subject: [PATCH] fix disassembly when $ed, $dd & $fd prefixes are used but the
 instruction is not valid. [smf]

---
 src/devices/cpu/z80/z80dasm.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/devices/cpu/z80/z80dasm.cpp b/src/devices/cpu/z80/z80dasm.cpp
index b59b3a38eb6..f579fd6d62d 100644
--- a/src/devices/cpu/z80/z80dasm.cpp
+++ b/src/devices/cpu/z80/z80dasm.cpp
@@ -416,6 +416,8 @@ offs_t z80_disassembler::disassemble(std::ostream &stream, offs_t pc, const data
 		break;
 	case 0xed:
 		d = &mnemonic_ed[opcodes.r8(pos++)];
+		if (d->mnemonic == zDB)
+			pos--;
 		break;
 	case 0xdd:
 	{
@@ -428,7 +430,11 @@ offs_t z80_disassembler::disassemble(std::ostream &stream, offs_t pc, const data
 			d = &mnemonic_xx_cb[op1];
 		}
 		else
+		{
 			d = &mnemonic_xx[op1];
+			if (d->mnemonic == zDB)
+				pos--;
+		}
 		break;
 	}
 	case 0xfd:
@@ -442,7 +448,11 @@ offs_t z80_disassembler::disassemble(std::ostream &stream, offs_t pc, const data
 			d = &mnemonic_xx_cb[op1];
 		}
 		else
+		{
 			d = &mnemonic_xx[op1];
+			if (d->mnemonic == zDB)
+				pos--;
+		}
 		break;
 	}
 	default: