The Intel 87C51 80C51BH 80C31BH is a single-chip control-oriented microcontroller which is fabricated on Intel's reliable CHMOS III-E technology Being a member of the MCS 51 controller family the 87C51 80C51BH 80C31BH uses the same powerful instruction set has the same architecture and is pin-forpin compatible with the existing MCS 51 controller family of products The 80C51BHP is identical to the 80C51BH When ordering the 80C51BHP customers must submit the 64 byte encryption table together with the ROM code Lock bit 1 will be set to enable the internal ROM code protection and at the same time allows code verification The extremely low operating power along with the two reduced power modes Idle and Power Down make this part very suitable for low power applications The Idle mode freezes the CPU while allowing the RAM timer counters serial port and interrupt system to continue functioning The Power Down mode saves the RAM contents but freezes the oscillator causing all other chip functions to be inoperative For the remainder of this document the 87C51 80C51BH and 80C31BH will be referred to as the 87C51 BH unless information applies to a specific device