diff --git a/configs/xtrs/include/board.h b/configs/xtrs/include/board.h
index 97282fe5558..7a3050d6f91 100644
--- a/configs/xtrs/include/board.h
+++ b/configs/xtrs/include/board.h
@@ -60,6 +60,9 @@ extern "C" {
 #define EXTERN extern
 #endif
 
+EXTERN void z80_lowputc(char ch) __naked;
+EXTERN char z80_lowgetc(void) __naked;
+
 #undef EXTERN
 #if defined(__cplusplus)
 }
diff --git a/configs/xtrs/nsh/defconfig b/configs/xtrs/nsh/defconfig
index 62d4047b309..d5467c86986 100644
--- a/configs/xtrs/nsh/defconfig
+++ b/configs/xtrs/nsh/defconfig
@@ -110,8 +110,13 @@ CONFIG_LINKER_CODE_AREA=0x5300
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=nsh
 CONFIG_DEBUG=n
@@ -125,7 +130,9 @@ CONFIG_START_YEAR=2007
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_CONSOLE=n
+CONFIG_DEV_LOWCONSOLE=n
 
 #
 # The following can be used to disable categories of
diff --git a/configs/xtrs/ostest/defconfig b/configs/xtrs/ostest/defconfig
index 4561837e0a9..e7cda9a360b 100644
--- a/configs/xtrs/ostest/defconfig
+++ b/configs/xtrs/ostest/defconfig
@@ -110,8 +110,13 @@ CONFIG_LINKER_CODE_AREA=0x5300
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=ostest
 CONFIG_DEBUG=n
@@ -125,7 +130,9 @@ CONFIG_START_YEAR=2008
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_CONSOLE=n
+CONFIG_DEV_LOWCONSOLE=n
 
 #
 # The following can be used to disable categories of
diff --git a/configs/xtrs/pashello/defconfig b/configs/xtrs/pashello/defconfig
index 824f86d023e..7246a8b164f 100644
--- a/configs/xtrs/pashello/defconfig
+++ b/configs/xtrs/pashello/defconfig
@@ -110,8 +110,13 @@ CONFIG_LINKER_CODE_AREA=0x5300
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=pashello
 CONFIG_DEBUG=n
@@ -125,6 +130,7 @@ CONFIG_START_YEAR=2008
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_CONSOLE=n
 CONFIG_DEV_LOWCONSOLE=n
 
diff --git a/configs/xtrs/src/xtr_lowputc.c b/configs/xtrs/src/xtr_lowputc.c
index be1628444e0..c85f540d2e4 100644
--- a/configs/xtrs/src/xtr_lowputc.c
+++ b/configs/xtrs/src/xtr_lowputc.c
@@ -77,10 +77,10 @@
  ********************************************************************************/
 
 /********************************************************************************
- * Name: up_lowputc
+ * Name: z80_lowputc
  ********************************************************************************/
 
-void up_lowputc(char ch) __naked
+void z80_lowputc(char ch) __naked
 {
   _asm
 	ld	hl, #2
@@ -92,10 +92,10 @@ void up_lowputc(char ch) __naked
 }
 
 /********************************************************************************
- * Name: up_lowgetc
+ * Name: z80_lowgetc
  ********************************************************************************/
 
-char up_lowgetc(void) __naked
+char z80_lowgetc(void) __naked
 {
   _asm
 	call    _TRS80_M3_KBDSCN	;0x002b
diff --git a/configs/xtrs/src/xtr_serial.c b/configs/xtrs/src/xtr_serial.c
index dbe69df678f..b6a90baf123 100644
--- a/configs/xtrs/src/xtr_serial.c
+++ b/configs/xtrs/src/xtr_serial.c
@@ -277,7 +277,7 @@ static int up_ioctl(struct file *filep, int cmd, unsigned long arg)
 
 static int up_receive(struct uart_dev_s *dev, uint32 *status)
 {
-//  uint8 ch = up_lowgetc();
+//  uint8 ch = z80_lowputc();
 
   *status = 0;
   return ch;
@@ -318,7 +318,7 @@ static boolean up_rxavailable(struct uart_dev_s *dev)
 
 static void up_send(struct uart_dev_s *dev, int ch)
 {
-  up_lowputc(ch);
+  z80_lowputc(ch);
 }
 
 /****************************************************************************
@@ -409,6 +409,6 @@ void up_serialinit(void)
 
 int up_putc(int ch)
 {
-  up_lowputc(ch);
+  z80_lowputc(ch);
   return 0;
 }
diff --git a/configs/z80sim/include/board.h b/configs/z80sim/include/board.h
index eb7aa36853c..4cc4b97daf8 100644
--- a/configs/z80sim/include/board.h
+++ b/configs/z80sim/include/board.h
@@ -55,6 +55,9 @@ extern "C" {
 #define EXTERN extern
 #endif
 
+EXTERN void z80_lowputc(char ch) __naked;
+EXTERN char z80_lowgetc(void) __naked;
+
 #undef EXTERN
 #if defined(__cplusplus)
 }
diff --git a/configs/z80sim/nsh/defconfig b/configs/z80sim/nsh/defconfig
index aa852ef8a5e..190f7af9c70 100644
--- a/configs/z80sim/nsh/defconfig
+++ b/configs/z80sim/nsh/defconfig
@@ -103,8 +103,13 @@ CONFIG_HAVE_LIBM=n
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=nsh
 CONFIG_DEBUG=n
@@ -118,7 +123,9 @@ CONFIG_START_YEAR=2007
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_CONSOLE=y
+CONFIG_DEV_LOWCONSOLE=n
 
 #
 # The following can be used to disable categories of
diff --git a/configs/z80sim/ostest/defconfig b/configs/z80sim/ostest/defconfig
index 50eaec58785..3907e75b7b1 100644
--- a/configs/z80sim/ostest/defconfig
+++ b/configs/z80sim/ostest/defconfig
@@ -103,8 +103,13 @@ CONFIG_HAVE_LIBM=n
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=ostest
 CONFIG_DEBUG=n
@@ -118,7 +123,9 @@ CONFIG_START_YEAR=2007
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_CONSOLE=n
+CONFIG_DEV_LOWCONSOLE=n
 
 #
 # The following can be used to disable categories of
diff --git a/configs/z80sim/pashello/defconfig b/configs/z80sim/pashello/defconfig
index e56c00e2a42..6f2649084aa 100644
--- a/configs/z80sim/pashello/defconfig
+++ b/configs/z80sim/pashello/defconfig
@@ -103,8 +103,13 @@ CONFIG_HAVE_LIBM=n
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=pashello
 CONFIG_DEBUG=n
@@ -119,7 +124,9 @@ CONFIG_START_MONTH=2
 CONFIG_START_DAY=21
 CONFIG_JULIAN_TIME=n
 CONFIG_DEV_CONSOLE=y
+CONFIG_HAVE_LOWUARTINIT=n
 CONFIG_DEV_LOWCONSOLE=y
+CONFIG_DEV_LOWCONSOLE=n
 
 #
 # The following can be used to disable categories of
diff --git a/configs/z80sim/src/z80_lowputc.c b/configs/z80sim/src/z80_lowputc.c
index 4996272f952..269d37f92b6 100644
--- a/configs/z80sim/src/z80_lowputc.c
+++ b/configs/z80sim/src/z80_lowputc.c
@@ -69,13 +69,13 @@
  ********************************************************************************/
 
 /********************************************************************************
- * Name: up_lowputc
+ * Name: z80_lowputc
  *
  * Data sent to port 0xbe are echoed on stdout by the simulation
  *
  ********************************************************************************/
 
-void up_lowputc(char ch) __naked
+void z80_lowputc(char ch) __naked
 {
   _asm
 	ld	hl, #2
@@ -87,13 +87,13 @@ void up_lowputc(char ch) __naked
 }
 
 /********************************************************************************
- * Name: up_lowgetc
+ * Name: z80_lowgetc
  *
  * Data from stdin can be received on port 0xbe in the simulation
  *
  ********************************************************************************/
 
-char up_lowgetc(void) __naked
+char z80_lowgetc(void) __naked
 {
   _asm
 	in	a, (0xbe)
diff --git a/configs/z80sim/src/z80_serial.c b/configs/z80sim/src/z80_serial.c
index 42b0eecc14e..974b51b8fd8 100644
--- a/configs/z80sim/src/z80_serial.c
+++ b/configs/z80sim/src/z80_serial.c
@@ -227,7 +227,7 @@ static int up_ioctl(struct file *filep, int cmd, unsigned long arg)
 
 static int up_receive(struct uart_dev_s *dev, uint32 *status)
 {
-  uint8 ch = up_lowgetc();
+  uint8 ch = z80_getputc();
   *status = 0;
   return ch;
 }
@@ -267,7 +267,7 @@ static boolean up_rxavailable(struct uart_dev_s *dev)
 
 static void up_send(struct uart_dev_s *dev, int ch)
 {
-  up_lowputc(ch);
+  z80_lowputc(ch);
 }
 
 /****************************************************************************
@@ -358,7 +358,7 @@ void up_serialinit(void)
 
 int up_putc(int ch)
 {
-  up_lowputc(ch);
+  z80_lowputc(ch);
   return 0;
 }
 
diff --git a/configs/z8encore000zco/ostest/defconfig b/configs/z8encore000zco/ostest/defconfig
index 7f864c45660..78b53262266 100644
--- a/configs/z8encore000zco/ostest/defconfig
+++ b/configs/z8encore000zco/ostest/defconfig
@@ -137,8 +137,13 @@ CONFIG_HAVE_LIBM=n
 # CONFIG_JULIAN_TIME - Enables Julian time conversions
 # CONFIG_START_YEAR, CONFIG_START_MONTH, CONFIG_START_DAY -
 #   Used to initialize the internal time logic.
+# CONFIG_HAVE_LOWUARTINIT - Provides low-level UART initialization
+#   logic as up_lowuartinit (only needed if there is no
+#   serial driver).
 # CONFIG_DEV_CONSOLE - Set if architecture-specific logic
 #   provides /dev/console.  Enables stdout, stderr, stdin.
+# CONFIG_DEV_LOWCONSOLE - Use the simple, low-level serial console
+#   driver (minimul support)
 #
 CONFIG_EXAMPLE=ostest
 CONFIG_DEBUG=y
@@ -152,6 +157,7 @@ CONFIG_START_YEAR=2008
 CONFIG_START_MONTH=2
 CONFIG_START_DAY=17
 CONFIG_JULIAN_TIME=n
+CONFIG_HAVE_LOWUARTINIT=y
 CONFIG_DEV_CONSOLE=n
 CONFIG_DEV_LOWCONSOLE=n