diff --git a/src/hei_signature.hpp b/src/hei_signature.hpp
index 4f824db..d4b40f4 100644
--- a/src/hei_signature.hpp
+++ b/src/hei_signature.hpp
@@ -25,9 +25,8 @@
      * @param i_bit      The target bit within this register.
      * @param i_attnType The attention type reported by this bit.
      */
-    Signature(const Chip& i_chip, RegisterId_t i_id,
-              RegisterInstance_t i_instance, RegisterBit_t i_bit,
-              AttentionType_t i_attnType) :
+    Signature(const Chip& i_chip, RegisterId_t i_id, Instance_t i_instance,
+              BitPosition_t i_bit, AttentionType_t i_attnType) :
         iv_chip(i_chip),
         iv_id(i_id), iv_instance(i_instance), iv_bit(i_bit),
         iv_attnType(i_attnType)
@@ -43,11 +42,11 @@
     Signature& operator=(const Signature&) = default;
 
   private:
-    Chip iv_chip;                   ///< Chip containing this register.
-    RegisterId_t iv_id;             ///< Register ID.
-    RegisterInstance_t iv_instance; ///< Instance of this register.
-    RegisterBit_t iv_bit;           ///< Target bit within this register.
-    AttentionType_t iv_attnType;    ///< Attention type reported by this bit.
+    Chip iv_chip;                ///< Chip containing this register.
+    RegisterId_t iv_id;          ///< Register ID.
+    Instance_t iv_instance;      ///< Instance of this register.
+    BitPosition_t iv_bit;        ///< Target bit within this register.
+    AttentionType_t iv_attnType; ///< Attention type reported by this bit.
 
   public: // Member functions
     /** @return The chip containing this register. */
@@ -63,13 +62,13 @@
     }
 
     /** @return The instance of this register. */
-    RegisterInstance_t getInstance() const
+    Instance_t getInstance() const
     {
         return iv_instance;
     }
 
     /** @return The target bit within this register. */
-    RegisterBit_t getBit() const
+    BitPosition_t getBit() const
     {
         return iv_bit;
     }
diff --git a/src/hei_types.hpp b/src/hei_types.hpp
index 7cb853a..13bc72f 100644
--- a/src/hei_types.hpp
+++ b/src/hei_types.hpp
@@ -25,7 +25,7 @@
  *   both the Chip Data Files and the input into the isolation function.
  *
  * Range:
- *   A 4-byte field should be sufficient.
+ *   This is defined as a 4-byte field in the Chip Data Files.
  */
 using ChipType_t = uint32_t;
 
@@ -39,68 +39,58 @@
  *   The supported register types are listed in this enum.
  *
  * Range:
- *   Power Systems only have a couple different types that would be accessed by
- *   the isolator. The minimum 1-byte field should be sufficient.
+ *   This is defined as the minimum 1-byte field in the Chip Data Files.
  */
 enum RegisterType_t : uint8_t
 {
-    REG_TYPE_INVALID = 0, ///< invalid/unsupported type
-    REG_TYPE_SCOM    = 1, ///< Power Systems SCOM register.
-    REG_TYPE_ID_SCOM = 2, ///< Power Systems Indirect SCOM register.
+    REG_TYPE_SCOM    = 0x01, ///< Power Systems SCOM register.
+    REG_TYPE_ID_SCOM = 0x02, ///< Power Systems Indirect SCOM register.
 };
 
 /**
  * Each register within a chip must have a unique ID. These IDs (combined with
  * other information) will be passed back to the user application to identify
- * all of the active errors reported by this chip. Note that some registers will
- * have multiple instances within a chip. An ID will be used for all instances
- * of a register. See enum RegisterInstance_t for details on the register
- * instance value.
+ * register contents captured for debugging purposes. Note that some registers
+ * will have multiple instances within a chip. An ID will be used for all
+ * instances of a register. See Instance_t for details on the register instance
+ * value.
  *
  * Values:
  *   The isolator does not need to know the possible values because the values
- *   are passed from the Chip Data Files to the user application. Therefore, no
- *   values will be listed in this enum except for the default invalid type.
+ *   are passed from the Chip Data Files to the user application.
  *
  * Range:
- *   A 2-byte field should be sufficient to support up to 65535 registers on a
- *   chip.
+ *   This is defined as a 3-byte field in the Chip Data Files, which should be
+ *   sufficient to support all the registers on a typical chip.
  */
-enum RegisterId_t : uint16_t
-{
-    REG_ID_INVALID = 0, ///< invalid/unsupported type
-};
+using RegisterId_t = uint32_t; // IMPORTANT: see range note above.
 
 /**
- * A chip could contain more than one instance of a register. For example, a
- * register could exist for each instance of a core on a processor chip.
- * This field will be used to differeniate multiple instances of a register in
- * order to avoid repeating common information for every instance.
+ * A chip could contain more than one instance of a register or node. For
+ * example, a register could exist for each instance of a core on a processor
+ * chip. This field will be used to differeniate multiple instances of a
+ * register in order to avoid repeating common information for every instance.
  *
  * Values:
- *   Not all registers will have multiple instances. So the default instance
- *   value is 0, which always indicates the first (or only) logical instance.
- *   Then a value of 1-255 can be used for each subsequent instance.
+ *   Not all registers or nodes will have multiple instances. So the default
+ *   instance value is 0, which always indicates the first (or only) logical
+ *   instance. Then a value of 1-255 can be used for each subsequent instance.
  *
  * Range:
- *   The 1-byte field should be sufficient.
+ *   This is defined as a 1-byte field in the Chip Data Files.
  */
-enum RegisterInstance_t : uint8_t
-{
-    REG_INST_DEFAULT = 0, ///< indicates the first (or only) logical instance
-};
+using Instance_t = uint8_t;
 
 /**
- * This is used to defined a bit field for a register. It is mainly used in the
- * Signature class to indicate which bit on a register had an active attention.
+ * This is used to defined a bit field for a register or node.
  *
  * Values:
- *   The widest supported register is only 64-bits (value 0-63).
+ *   The widest supported register type is only 64-bits (value 0-63).
  *
  * Range:
- *   Only the minimum 1-byte field is necessary.
+ *   This is defined as a 1-byte field in the Chip Data Files.
  */
-typedef uint8_t RegisterBit_t;
+using BitPosition_t = uint8_t;
 
 /**
  * The hardware address of a register (right justified).
@@ -111,10 +101,7 @@
  * Range:
  *   The maximum supported address requires an 8-byte field.
  */
-enum RegisterAddress_t : uint64_t
-{
-    REG_ADDR_INVALID = 0, ///< invalid/unsupported address
-};
+using RegisterAddress_t = uint64_t;
 
 /**
  * The hardware access level of a register.
@@ -123,7 +110,7 @@
  *   The supported access levels are listed in this enum.
  *
  * Range:
- *   Only the minimum 1-byte field is necessary.
+ *   This is defined as a 1-byte field in the Chip Data Files.
  */
 enum RegisterAccessLevel_t : uint8_t
 {
@@ -143,7 +130,7 @@
  *   The supported attention types are listed in this enum.
  *
  * Range:
- *   Only the minimum 1-byte field is necessary.
+ *   This is defined as a 1-byte field in the Chip Data Files.
  */
 enum AttentionType_t : uint8_t
 {
diff --git a/src/isolator/hei_isolation_node.cpp b/src/isolator/hei_isolation_node.cpp
index e2bf61a..f5c58db 100644
--- a/src/isolator/hei_isolation_node.cpp
+++ b/src/isolator/hei_isolation_node.cpp
@@ -21,10 +21,10 @@
     const BitString* bs = rule_itr->second->getBitString(i_chip);
 
     // Ensure this BitString is not longer than the maximum bit field.
-    HEI_ASSERT(bs->getBitLen() <= (1 << (sizeof(RegisterBit_t) * 8)));
+    HEI_ASSERT(bs->getBitLen() <= (1 << (sizeof(BitPosition_t) * 8)));
 
     // Find all active bits for this rule.
-    for (RegisterBit_t bit = 0; bit < bs->getBitLen(); bit++)
+    for (BitPosition_t bit = 0; bit < bs->getBitLen(); bit++)
     {
         // Continue to the next bit if not active.
         if (!bs->isBitSet(bit))
diff --git a/src/isolator/hei_isolation_node.hpp b/src/isolator/hei_isolation_node.hpp
index eedde91..782ac7f 100644
--- a/src/isolator/hei_isolation_node.hpp
+++ b/src/isolator/hei_isolation_node.hpp
@@ -89,7 +89,7 @@
      * Each bit (key) in this map indicates that an attention was driven from
      * another register (value).
      */
-    std::map<RegisterBit_t, const IsolationNode*> iv_children;
+    std::map<BitPosition_t, const IsolationNode*> iv_children;
 
   public: // Member functions
     /**
@@ -136,7 +136,7 @@
      * @param The target bit on this register.
      * @param The child register to analyze for the given bit.
      */
-    void addChild(RegisterBit_t i_bit, const IsolationNode* i_child);
+    void addChild(BitPosition_t i_bit, const IsolationNode* i_child);
 
   public: // Operators
     /** @brief Equals operator. */
diff --git a/src/register/hei_hardware_register.hpp b/src/register/hei_hardware_register.hpp
index 40e0f82..81fb79b 100644
--- a/src/register/hei_hardware_register.hpp
+++ b/src/register/hei_hardware_register.hpp
@@ -49,7 +49,7 @@
      * @param i_accessLevel Hardware access level for this register.
      */
     HardwareRegister(ChipType_t i_chipType, RegisterId_t i_id,
-                     RegisterInstance_t i_instance,
+                     Instance_t i_instance,
                      RegisterAccessLevel_t i_accessLevel) :
         Register(),
         iv_chipType(i_chipType), iv_id(i_id), iv_instance(i_instance),
@@ -66,7 +66,7 @@
     /** A register may have multiple instances. All of which will have the same
      *  ID. This variable is used to distinguish between each instance of the
      *  register. */
-    const RegisterInstance_t iv_instance;
+    const Instance_t iv_instance;
 
     /** The hardware access level of this register (read/write, read-only,
      *  write-only, etc.). */
@@ -86,7 +86,7 @@
     }
 
     /* @return The instance of this register. */
-    RegisterInstance_t getInstance() const
+    Instance_t getInstance() const
     {
         return iv_instance;
     }
diff --git a/src/register/hei_scom_register.hpp b/src/register/hei_scom_register.hpp
index 3723a58..b93674a 100644
--- a/src/register/hei_scom_register.hpp
+++ b/src/register/hei_scom_register.hpp
@@ -25,8 +25,8 @@
      * @param i_address     A 4-byte address for this SCOM register.
      */
     ScomRegister(ChipType_t i_chipType, RegisterId_t i_id,
-                 RegisterInstance_t i_instance,
-                 RegisterAccessLevel_t i_accessLevel, uint32_t i_address) :
+                 Instance_t i_instance, RegisterAccessLevel_t i_accessLevel,
+                 uint32_t i_address) :
         HardwareRegister(i_chipType, i_id, i_instance, i_accessLevel),
         iv_address(i_address)
     {}
@@ -106,8 +106,8 @@
      * @param i_address     An 8-byte address for this Indirect SCOM register.
      */
     IdScomRegister(ChipType_t i_chipType, RegisterId_t i_id,
-                   RegisterInstance_t i_instance,
-                   RegisterAccessLevel_t i_accessLevel, uint64_t i_address) :
+                   Instance_t i_instance, RegisterAccessLevel_t i_accessLevel,
+                   uint64_t i_address) :
         HardwareRegister(i_chipType, i_id, i_instance, i_accessLevel),
         iv_address(i_address)
     {}