diff --git a/stm8s.h b/stm8s.h
index 232a1b9..cf26336 100644
--- a/stm8s.h
+++ b/stm8s.h
@@ -3294,26 +3294,31 @@ typedef union {
 	uint8_t reg; /*!< type used for register access */
 } OPT_NOPT1_type; /*!<  */
 
+// NOTE: OPT2 fields depends on device's pin count
 typedef union {
 	struct {
-		uint8_t :1; /*!< bit 0: Reserved */
+		uint8_t AFR0:1; /*!< bit 0: Alternate function remapping option 0 */
 		uint8_t AFR1:1; /*!< bit 1: Alternate function remapping option 1 */
-		uint8_t :3; /*!< bit 2..4: Reserved */
+		uint8_t AFR2:1; /*!< bit 2: Alternate function remapping option 2 */
+		uint8_t AFR3:1; /*!< bit 3: Alternate function remapping option 3 */
+		uint8_t AFR4:1; /*!< bit 4: Alternate function remapping option 4 */
 		uint8_t AFR5:1; /*!< bit 5: Alternate function remapping option 5 */
 		uint8_t AFR6:1; /*!< bit 6: Alternate function remapping option 6 */
-		uint8_t :1; /*!< bit 7: Reserved */
+		uint8_t AFR7:1; /*!< bit 7: Alternate function remapping option 7 */
 	} fields; /*!< structure used for bit access */
 	uint8_t reg; /*!< type used for register access */
 } OPT_OPT2_type; /*!<  */
 
 typedef union {
 	struct {
-		uint8_t :1; /*!< bit 0: Reserved */
+		uint8_t NAFR0:1; /*!< bit 0: Alternate function remapping option 0 */
 		uint8_t NAFR1:1; /*!< bit 1: Alternate function remapping option 1 */
-		uint8_t :3; /*!< bit 2..4: Reserved */
+		uint8_t NAFR2:1; /*!< bit 2: Alternate function remapping option 2 */
+		uint8_t NAFR3:1; /*!< bit 3: Alternate function remapping option 3 */
+		uint8_t NAFR4:1; /*!< bit 4: Alternate function remapping option 4 */
 		uint8_t NAFR5:1; /*!< bit 5: Alternate function remapping option 5 */
 		uint8_t NAFR6:1; /*!< bit 6: Alternate function remapping option 6 */
-		uint8_t :1; /*!< bit 7: Reserved */
+		uint8_t NAFR7:1; /*!< bit 7: Alternate function remapping option 7 */
 	} fields; /*!< structure used for bit access */
 	uint8_t reg; /*!< type used for register access */
 } OPT_NOPT2_type; /*!<  */