From c4e8f00006865da3d6c6863cd559573556573fc3 Mon Sep 17 00:00:00 2001
From: AJR <ajrhacker@users.noreply.github.com>
Date: Mon, 11 Oct 2021 17:13:37 -0400
Subject: [PATCH] hd6120: IAC also complements LINK on carry out

---
 src/devices/cpu/pdp8/hd6120.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/devices/cpu/pdp8/hd6120.cpp b/src/devices/cpu/pdp8/hd6120.cpp
index dccd84ad526..769a41d8b5b 100644
--- a/src/devices/cpu/pdp8/hd6120.cpp
+++ b/src/devices/cpu/pdp8/hd6120.cpp
@@ -664,7 +664,13 @@ void hd6120_device::execute_run()
 
 		case minor_state::OP1_1:
 			m_pc = m_temp & 07777;
-			m_temp = ((BIT(m_ir, 7) ? 0 : m_ac) ^ (BIT(m_ir, 5) ? 07777 : 0)) + (m_ir & 0001);
+			m_temp = (BIT(m_ir, 7) ? 0 : m_ac) ^ (BIT(m_ir, 5) ? 07777 : 0);
+			if (BIT(m_ir, 0))
+			{
+				++m_temp;
+				if (m_temp >= 010000)
+					m_flags ^= 4; // LINK is complemented upon carry out
+			}
 			m_state = minor_state::OP1_2;
 			break;