diff --git a/src/devices/cpu/nec/v25.cpp b/src/devices/cpu/nec/v25.cpp
index 2333a525d9b..da7f194318d 100644
--- a/src/devices/cpu/nec/v25.cpp
+++ b/src/devices/cpu/nec/v25.cpp
@@ -52,7 +52,7 @@ const device_type V35 = &device_creator<v35_device>;
 v25_common_device::v25_common_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock, const char *shortname, bool is_16bit, offs_t fetch_xor, UINT8 prefetch_size, UINT8 prefetch_cycles, UINT32 chip_type)
 	: cpu_device(mconfig, type, name, tag, owner, clock, shortname, __FILE__)
 	, m_program_config("program", ENDIANNESS_LITTLE, is_16bit ? 16 : 8, 20, 0)
-	, m_io_config("io", ENDIANNESS_LITTLE, is_16bit ? 16 : 8, 17, 0)
+	, m_io_config("io", ENDIANNESS_LITTLE, is_16bit ? 16 : 8, 16+1, 0)
 	, m_fetch_xor(fetch_xor)
 	, m_PCK(8)
 	, m_prefetch_size(prefetch_size)
diff --git a/src/devices/cpu/pps4/pps4.cpp b/src/devices/cpu/pps4/pps4.cpp
index 5ae8e822846..b2a6cc8129f 100644
--- a/src/devices/cpu/pps4/pps4.cpp
+++ b/src/devices/cpu/pps4/pps4.cpp
@@ -74,7 +74,7 @@ pps4_device::pps4_device(const machine_config &mconfig, const char *tag, device_
 	: cpu_device(mconfig, PPS4, "PPS4", tag, owner, clock, "pps4", __FILE__ )
 	, m_program_config("program", ENDIANNESS_LITTLE, 8, 12)
 	, m_data_config("data", ENDIANNESS_LITTLE, 8, 12)  // 4bit RAM
-	, m_io_config("io", ENDIANNESS_LITTLE, 8, 8)  // 4bit IO
+	, m_io_config("io", ENDIANNESS_LITTLE, 8, 8+1)  // 4bit IO
 {
 }
 
diff --git a/src/devices/cpu/tms32010/tms32010.cpp b/src/devices/cpu/tms32010/tms32010.cpp
index 332f09c9dc0..ab49c52b603 100644
--- a/src/devices/cpu/tms32010/tms32010.cpp
+++ b/src/devices/cpu/tms32010/tms32010.cpp
@@ -102,7 +102,7 @@ tms32010_device::tms32010_device(const machine_config &mconfig, const char *tag,
 	: cpu_device(mconfig, TMS32010, "TMS32010", tag, owner, clock, "tms32010", __FILE__)
 	, m_program_config("program", ENDIANNESS_BIG, 16, 12, -1)
 	, m_data_config("data", ENDIANNESS_BIG, 16, 8, -1, ADDRESS_MAP_NAME(tms32010_ram))
-	, m_io_config("io", ENDIANNESS_BIG, 16, 5, -1)
+	, m_io_config("io", ENDIANNESS_BIG, 16, 4+1, -1)
 	, m_addr_mask(0x0fff)
 {
 }
@@ -112,7 +112,7 @@ tms32010_device::tms32010_device(const machine_config &mconfig, device_type type
 	: cpu_device(mconfig, type, name, tag, owner, clock, shortname, source)
 	, m_program_config("program", ENDIANNESS_BIG, 16, 12, -1)
 	, m_data_config("data", ENDIANNESS_BIG, 16, 8, -1, ADDRESS_MAP_NAME(tms32015_ram))
-	, m_io_config("io", ENDIANNESS_BIG, 16, 5, -1)
+	, m_io_config("io", ENDIANNESS_BIG, 16, 4+1, -1)
 	, m_addr_mask(addr_mask)
 {
 }
diff --git a/src/devices/cpu/tms32025/tms32025.cpp b/src/devices/cpu/tms32025/tms32025.cpp
index cd95f1a96c8..c202c243ea2 100644
--- a/src/devices/cpu/tms32025/tms32025.cpp
+++ b/src/devices/cpu/tms32025/tms32025.cpp
@@ -212,7 +212,7 @@ tms32025_device::tms32025_device(const machine_config &mconfig, const char *tag,
 	: cpu_device(mconfig, TMS32025, "TMS32025", tag, owner, clock, "tms32025", __FILE__)
 	, m_program_config("program", ENDIANNESS_BIG, 16, 16, -1)
 	, m_data_config("data", ENDIANNESS_BIG, 16, 16, -1)
-	, m_io_config("io", ENDIANNESS_BIG, 16, 17, -1)
+	, m_io_config("io", ENDIANNESS_BIG, 16, 16+1, -1)
 {
 }
 
@@ -221,7 +221,7 @@ tms32025_device::tms32025_device(const machine_config &mconfig, device_type type
 	: cpu_device(mconfig, type, name, tag, owner, clock, shortname, source)
 	, m_program_config("program", ENDIANNESS_BIG, 16, 16, -1)
 	, m_data_config("data", ENDIANNESS_BIG, 16, 16, -1)
-	, m_io_config("io", ENDIANNESS_BIG, 16, 16, -1)
+	, m_io_config("io", ENDIANNESS_BIG, 16, 16+1, -1)
 {
 }