. Electronic Components Datasheets 80c51 fam prog guide 1 free download

File name 80c51_fam_prog_guide_1.pdf

Philips Semiconductors 80C51 family programmer's guide 80C51 Family and instruction set PROGRAMMER'S GUIDE AND INSTRUCTION SET register bank contains eight 1-byte registers 0 through 7. Reset initializes the stack pointer to location 07H, and it is incremented Memory Organization once to start from location 08H, which is the first register (R0) of the second register bank. Thus, in order to use more than one Program Memory register bank, the SP should be initialized to a different location The 80C51 has separate address spaces for program and data of the RAM where it is not used for data storage (i.e., the higher memory. The Program memory can be up to 64k bytes long. The part of the RAM). lower 4k can reside on-chip. Figure 1 shows a map of the 80C51 program memory. 2. Bit Addressable Area: 16 bytes have been assigned for this segment, 20H-2FH. Each one of the 128 bits of this segment can The 80C51 can address up to 64k bytes of data memory to the chip. be directly addressed (0-7FH). The bits can be referred to in two The MOVX instruction is used to access the external data memory. ways, both of which are acceptable by most assemblers. One The 80C51 has 128 bytes of on-chip RAM, plus a number of Special way is to refer to their address (i.e., 0-7FH). The other way is Function Registers (SFRs). The lower 128 bytes of RAM can be with reference to bytes 20H to 2FH. Thus, bits 0-7 can also be accessed either by direct addressing (MOV data addr) or by indirect referred to as bits 20.0-20.7, and bits 8-FH are the same as addressing (MOV @Ri). Figure 2 shows the Data Memory 21.0-21.7, and so on. Each of the 16 bytes in this segment can organization. also be addressed as a byte. 3. Scratch Pad Area: 30H through 7FH are available to the user as Direct and Indirect Address Area data RAM. However, if the stack pointer has been initialized to The 128 bytes of RAM which can be accessed by both direct and this area, enough b