8051 is also known as a MCS-51 which is developed by Intel in 1980. It has 8-bit CPU, memory, timers, counters, interrupt controller and serial I/O are highly integrated on single chip. It is a 40-pin IC. It has 4 byte input-output port, EEPROM of 4KB and RAM of 128 bytes. Pin diagram and architecture of 8051 is shown below.
Memory Space:
There are five memory spaces in 8051 which are...
1) Program memory
2) Internal data memory
3) External data memory
4) Special function registers
5) Bit memory
Program memory space is addressed by the 16-bit program counter register which holds the address of memory location from where instruction code is need to be fetched. It can also be addressed by the 16-bit DPTR (data pointer register) using few instruction. It primarily stores instruction code, constant data, constant tables and string.
Internal memory space stores all the variables and data structure which is directly operated by the program. It is functionally the most important data memory space. It contains four bank of general purpose registers and program counter.
External data memory space contains those data which can't fits on the chip. It addressed by the DPTR register. It can also be accessed by the first two general purpose register R0 and R1. This memory space is only accessed by the indirect addressing mode.
Special function registers space contains on chip peripheral I/O registers as well as some special registers which must be programmed to control and perform particular task. This SFRs can only be accessed by direct addressing mode.
Bit memory space is used for storing flags and bit variable. There is some specific instruction by which bit memory space can be accessible. It can also be addressed by direct addressing mode. This memory space is mostly used with decision making process.
Features of 8051:
1) 8-bit Arithmetic and logic unit
Disadvantage of 8051:
1) Limited on chip program and data memory 4kb and 128bytes respectively
There are five memory spaces in 8051 which are...
1) Program memory
2) Internal data memory
3) External data memory
4) Special function registers
5) Bit memory
Program memory space is addressed by the 16-bit program counter register which holds the address of memory location from where instruction code is need to be fetched. It can also be addressed by the 16-bit DPTR (data pointer register) using few instruction. It primarily stores instruction code, constant data, constant tables and string.
Internal memory space stores all the variables and data structure which is directly operated by the program. It is functionally the most important data memory space. It contains four bank of general purpose registers and program counter.
External data memory space contains those data which can't fits on the chip. It addressed by the DPTR register. It can also be accessed by the first two general purpose register R0 and R1. This memory space is only accessed by the indirect addressing mode.
Special function registers space contains on chip peripheral I/O registers as well as some special registers which must be programmed to control and perform particular task. This SFRs can only be accessed by direct addressing mode.
Bit memory space is used for storing flags and bit variable. There is some specific instruction by which bit memory space can be accessible. It can also be addressed by direct addressing mode. This memory space is mostly used with decision making process.
Features of 8051:
1) 8-bit Arithmetic and logic unit
2) 8-bit data and 16-bit data address bus.
3) Capability of address 64kb memory location
4) 128bytes on chip RAM i.e data memory
5) 4kb on chip ROM i.e program memory
6) Four 8-bit input/output port
7) Serial port (UART)
8) Two level interrupt priorities
9) Two 16-bit Timers/Counters
Disadvantage of 8051:
1) Limited on chip program and data memory 4kb and 128bytes respectively
2) No watchdog timer
3) It does not support ISP i.e in system programming
To over come this problems some company manufactures wide variety of chip which has 80c51 CPU as a heart (or i would say mind). For best chip which has 80c51 CPU click here...
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