diff --git a/src/MCP7940.h b/src/MCP7940.h
index 2a8e885..b6aea6e 100644
--- a/src/MCP7940.h
+++ b/src/MCP7940.h
@@ -56,10 +56,8 @@
   /*****************************************************************************************************************
   ** Declare constants used in the class                                                                          **
   *****************************************************************************************************************/
-  const uint16_t I2C_STANDARD_MODE         =    100000;                       // Default normal I2C comms speed   //
+  const uint16_t I2C_STANDARD_MODE         =    100000;                       // Default normal I2C 100KHz speed  //
   const uint16_t I2C_FAST_MODE             =    400000;                       // Fast mode                        //
-  const uint16_t I2C_FAST_MODE_PLUS_MODE   =   1000000;                       // Really fast mode                 //
-  const uint16_t I2C_HIGH_SPEED_MODE       =   3400000;                       // Turbo mode                       //
   const uint8_t  MCP7940_ADDRESS           =      0x6F;                       // Device address, fixed value      //
   const uint8_t  MCP7940_RTCSEC            =      0x00;                       // Register definitions             //
   const uint8_t  MCP7940_RTCMIN            =      0x01;                       //                                  //