P80C51 Microcontroller - 8 Bit - 40 Pin

The 80C51 has separate address spaces for program and data memory. The Program memory can be up to 64k bytes long. The lower 4k can reside on-chip. Figure 1 shows a map of the 80C51 program memory. The 80C51 can address up to 64k bytes of data memory to the chip. The MOVX instruction is used to access the external data memory. The 80C51 has 128 bytes of on-chip RAM, plus a number of special function Registers (SFRs). The lower 128 bytes of RAM can be accessed either by direct addressing (MOV data addr) or by indirect addressing (MOV @Ri).