From 79f85a600a5d35b8195c6d418e5842d515e00c3a Mon Sep 17 00:00:00 2001
From: mamehaze <140764005+mamehaze@users.noreply.github.com>
Date: Fri, 20 Sep 2024 18:26:31 +0100
Subject: cpu/xa: Implemented add with indexed addressing mode for source.
 (#12795)

Used by the tripfevb microcontroller program.
The game no longer causes a fatal error, but hangs instead.
---
 src/devices/cpu/xa/xa_ops.cpp | 2 +-
 src/mame/igs/igs_m027xa.cpp   | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/devices/cpu/xa/xa_ops.cpp b/src/devices/cpu/xa/xa_ops.cpp
index ae803581380..c66277ba6c4 100644
--- a/src/devices/cpu/xa/xa_ops.cpp
+++ b/src/devices/cpu/xa/xa_ops.cpp
@@ -1123,7 +1123,7 @@ void xa_cpu::aluop_byte_rd_rsoff8(int alu_op, u8 rd, u8 rs, u8 offset8)
 	}
 }
 
-void xa_cpu::add_word_rd_rsoff8(u8 rd, u8 rs, u8 offset8) { fatalerror("ADD.w %s, [%s+#$%02x]", m_regnames16[rd], m_regnames16[rs], offset8);}
+void xa_cpu::add_word_rd_rsoff8(u8 rd, u8 rs, u8 offset8) { u16 rdval = gr16(rd); u16 fulloffset = util::sext(offset8, 8); u16 address = get_addr(rs) + fulloffset; u16 val = rdat16(address); u16 result = do_add_16(rdval, val); sr16(rd, result); cy(6); }
 void xa_cpu::addc_word_rd_rsoff8(u8 rd, u8 rs, u8 offset8){ fatalerror("ADDC.w %s, [%s+#$%02x]", m_regnames16[rd], m_regnames16[rs], offset8);}
 void xa_cpu::sub_word_rd_rsoff8(u8 rd, u8 rs, u8 offset8) { fatalerror("SUB.w %s, [%s+#$%02x]", m_regnames16[rd], m_regnames16[rs], offset8);}
 void xa_cpu::subb_word_rd_rsoff8(u8 rd, u8 rs, u8 offset8){ fatalerror("SUBB.w %s, [%s+#$%02x]", m_regnames16[rd], m_regnames16[rs], offset8);}
diff --git a/src/mame/igs/igs_m027xa.cpp b/src/mame/igs/igs_m027xa.cpp
index aad61fb20af..5b01be7adcf 100644
--- a/src/mame/igs/igs_m027xa.cpp
+++ b/src/mame/igs/igs_m027xa.cpp
@@ -6,8 +6,8 @@
 IGS ARM7 (IGS027A) based Mahjong / Gambling platform(s) with XA sub-cpu
 These games use the IGS027A processor.
 
-Triple Fever (V105US) (tripfevb) causes MAME to exit with
-"Fatal error: ADD.w R0, [R7+#$02]" after paying out tickets.
+Triple Fever (V105US) (tripfevb) hangs after paying out tickets, with the MCU
+apparently attempting serial communication with something.
 
 */
 
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