diff --git a/arch/arm/src/kinetis/Kconfig b/arch/arm/src/kinetis/Kconfig
index 962dda4ee94..e88a31bf42b 100644
--- a/arch/arm/src/kinetis/Kconfig
+++ b/arch/arm/src/kinetis/Kconfig
@@ -713,6 +713,21 @@ config KINETIS_ENET_NORXER
 		If selected, then the MII/RMII RXER output will be configured as a
 		GPIO and pulled low.
 
+choice
+	prompt "RMII Clock Source"
+	default KINETIS_EMAC_RMIICLKEXTAL
+	depends on !KINETIS_ENETUSEMII && (ARCH_FAMILY_K64 || ARCH_FAMILY_K66)
+	---help---
+		The RMII clock can be selected between EXTAL or ENET_1588_CLKIN
+
+config KINETIS_EMAC_RMIICLKEXTAL
+	bool "Use EXTAL for RMII Clock"
+
+config KINETIS_EMAC_RMIICLK1588CLKIN
+	bool "Use ENET_1588_CLKIN for RMII Clock"
+
+endchoice # RMII Clock Source
+
 choice
 	prompt "Work queue"
 	default KINETIS_EMAC_LPWORK if SCHED_LPWORK
diff --git a/arch/arm/src/kinetis/chip/kinetis_sim.h b/arch/arm/src/kinetis/chip/kinetis_sim.h
index ae56504ff08..4b9a2ebe5f2 100644
--- a/arch/arm/src/kinetis/chip/kinetis_sim.h
+++ b/arch/arm/src/kinetis/chip/kinetis_sim.h
@@ -1,8 +1,9 @@
 /************************************************************************************
  * arch/arm/src/kinetis/chip/kinetis_sim.h
  *
- *   Copyright (C) 2011, 2016 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *   Copyright (C) 2011, 2016, 2017 Gregory Nutt. All rights reserved.
+ *   Authors: Gregory Nutt <gnutt@nuttx.org>
+ *            David Sidrane <david_s5@nscdg.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -136,8 +137,17 @@
                                                 /* Bit 17: Reserved */
 #define SIM_SOPT2_USBSRC              (1 << 18) /* Bit 18: USB clock source select */
                                                 /* Bit 19: Reserved */
-#ifdef KINETIS_K60
-#  define SIM_SOPT2_TIMESRC           (1 << 20) /* Bit 20: IEEE 1588 timestamp clock source select (K60) */
+#if defined(KINETIS_K60) || defined(KINETIS_K64) || defined(KINETIS_K66)
+#  define SIM_SOPT2_RMIISRC_SHIFT     (19)      /* Bit 19: RMII clock source select */
+#  define SIM_SOPT2_RMIISRC_EXTAL     (0 << SIM_SOPT2_RMIISRC_SHIFT) /* EXTAL clock */
+#  define SIM_SOPT2_RMIISRC_EXTBYP    (1 << SIM_SOPT2_RMIISRC_SHIFT) /* External bypass clock (ENET_1588_CLKIN) */
+#  define SIM_SOPT2_TIMESRC_SHIFT     (20)      /* Bit 20-21: IEEE 1588 timestamp clock source select (K60) */
+#  define SIM_SOPT2_TIMESRC_MASK      (3 << SIM_SOPT2_TIMESRC_SHIFT)
+#  define SIM_SOPT2_TIMESRC_CORE      (0 << SIM_SOPT2_TIMESRC_SHIFT) /* Core/system clock */
+#  define SIM_SOPT2_TIMESRC_PLLSEL    (1 << SIM_SOPT2_TIMESRC_SHIFT) /* MCGFLLCLK,MCGPLLCLK,IRC48M,USB1 PFD
+                                                                        clock as selected by SOPT2[PLLFLLSEL] */
+#  define SIM_SOPT2_TIMESRC_OSCERCLK  (2 << SIM_SOPT2_TIMESRC_SHIFT) /* OSCERCLK clock */
+#  define SIM_SOPT2_TIMESRC_EXTBYP    (0 << SIM_SOPT2_TIMESRC_SHIFT) /* External bypass clock (ENET_1588_CLKIN) */
 #endif
                                                 /* Bits 12-23: Reserved */
 #define SIM_SOPT2_I2SSRC_SHIFT        (24)      /* Bits 24-25: I2S master clock source select */
diff --git a/arch/arm/src/kinetis/kinetis_enet.c b/arch/arm/src/kinetis/kinetis_enet.c
index 8d4bcc11e9b..b1d83352a69 100644
--- a/arch/arm/src/kinetis/kinetis_enet.c
+++ b/arch/arm/src/kinetis/kinetis_enet.c
@@ -1,8 +1,9 @@
 /****************************************************************************
  * arch/arm/src/kinetis/kinetis_enet.c
  *
- *   Copyright (C) 2011-2012, 2014-2016 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *   Copyright (C) 2011-2012, 2014-2017 Gregory Nutt. All rights reserved.
+ *   Authors: Gregory Nutt <gnutt@nuttx.org>
+ *            David Sidrane <david_s5@nscdg.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -200,6 +201,17 @@
 
 #define KINETIS_BUF_SIZE  ((CONFIG_NET_ETH_MTU & 0xfffffff0) + 0x10)
 
+/* If this SoC has the RMII Clock Source selection configure it */
+
+#if defined(CONFIG_KINETIS_EMAC_RMIICLKEXTAL)
+#  define SIM_SOPT2_RMIISRC SIM_SOPT2_RMIISRC_EXTAL
+#endif
+
+#if defined(CONFIG_KINETIS_EMAC_RMIICLK1588CLKIN)
+#  define SIM_SOPT2_RMIISRC SIM_SOPT2_RMIISRC_EXTBYP
+#endif
+
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -1989,6 +2001,21 @@ int kinetis_netinitialize(int intf)
   DEBUGASSERT(intf < CONFIG_KINETIS_ENETNETHIFS);
   priv = &g_enet[intf];
 
+#if defined(SIM_SOPT2_RMIISRC)
+  /* If this Soc has RMII clock select then select the RMII clock source.
+   * First if the source is ENET_1588_CLKIN - configure the pin to apply the
+   * clock to the block. Then select it as the source.
+   */
+
+#  if SIM_SOPT2_RMIISRC == SIM_SOPT2_RMIISRC_EXTBYP
+  kinetis_pinconfig(PIN_ENET_1588_CLKIN);
+#  endif
+
+  regval  = getreg32(KINETIS_SIM_SOPT2);
+  regval |= SIM_SOPT2_RMIISRC;
+  putreg32(regval, KINETIS_SIM_SOPT2);
+#endif
+
   /* Enable the ENET clock */
 
   regval  = getreg32(KINETIS_SIM_SCGC2);