The MCSÉ 51 CHMOS microcontroller products are fabricated on Intel's reliable CHMOS process and are functionally compatible with the standard MCS 51 HMOS microcontroller products. This technology combines the high speed and density characteristics of HMOS with the low power attributes of CHMOS. This combination expands the effectiveness of the powerful MCS 51 microcontroller architecture and instruction set.
Like the MCS 51 HMOS microcontroller versions, the MCS 51 CHMOS microcontroller products have the following features: 4 Kbytes of EPROM/ROM (87C51/80C51BH respectively); 128 bytes of RAM; 32 I/O lines; two 16-bit timer/counters; a five-source two-level interrupt structure; a full duplex serial port; and on-chip oscillator and clock circuitry. In addition, the MCS 51 CHMOS microcontroller products exhibit low operating power, along with two software selectable modes of reduced activity for further power reductionÐIdle and Power Down.
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. The 87C51 is the EPROM version of the 80C51BH. It contains 4 Kbytes of on-chip program memory that can be electrically programmed, and can be erased by exposure to ultraviolet light. The 87C51 EPROM array uses a modified Quick-Pulse Programming algorithm, by which the entire 4 Kbyte array can be programmed in about 12 seconds.