From 91c2cf74d945e6408218edde9d98fbe4ab17526b Mon Sep 17 00:00:00 2001
From: Olivier Galibert <galibert@pobox.com>
Date: Mon, 24 Feb 2020 22:27:45 +0100
Subject: [PATCH] Possibly controversial i2cmem change, please lemme know if
 something breaks (nw)

---
 src/devices/machine/i2cmem.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/devices/machine/i2cmem.cpp b/src/devices/machine/i2cmem.cpp
index f7ab143d5b9..c32bd578ff3 100644
--- a/src/devices/machine/i2cmem.cpp
+++ b/src/devices/machine/i2cmem.cpp
@@ -344,7 +344,13 @@ WRITE_LINE_MEMBER( i2cmem_device::write_scl )
 					switch( m_state )
 					{
 					case STATE_DEVSEL:
-						m_devsel = m_shift;
+						if( m_shift & 1 )
+						{
+							verboselog( this, 1, "switching to read\n");
+							m_devsel &= 0x0e;
+							m_devsel |= (m_shift & 0xf1);
+						}
+						else m_devsel = m_shift;
 
 						if( !select_device() )
 						{
@@ -507,6 +513,13 @@ int i2cmem_device::select_device()
 	int device = ( m_slave_address & 0xf0 ) | ( m_e2 << 3 ) | ( m_e1 << 2 ) | ( m_e0 << 1 );
 	int mask = DEVSEL_ADDRESS & ~( address_mask() >> 7 );
 
+	if( m_devsel == 0 )
+	{
+		verboselog( this, 2, "acknowledging global call\n");
+		m_sdar = 0;
+		return 1;
+	}
+
 	if( ( m_devsel & mask ) == ( device & mask ) )
 	{
 		return 1;