8051 microcontrollers
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8051 microcontrollers
This microcontroller is also called as “System on a chip” because it has all the features on a single chip. The Block Diagram of 8051 Microcontroller is as shown in Figure
Image credit : EngineersGarage
AT89C51 (Variant of 8051 microcontroller) from Atmel Corporation
1 (‘C’ in the part number indicates CMOS). The flash memory can erase the contents within seconds which is best for fast growth. Therefore, 8751 is replaced by AT89C51 to eradicate the waiting time required to erase the contents and hence expedite the development time. To build up a microcontroller based system using AT89C51, it is essential to have ROM burner that supports flash memory. Note that in Flash memory, entire contents must be erased to program it again. The contents are erased by the ROM burner. Atmel is working on a newer version of AT89C51 that can be programmed using the serial COM port of IBM PC in order to get rid of the ROM burner.
Various 8051 microcontrollers
Part Number | ROM | RAM | I/O pins | Timer | Interrupt | Vcc | Packaging |
AT89C51 | 4K | 128 | 32 | 2 | 6 | 5V | 40 |
AT89C52 | 8K | 256 | 32 | 3 | 8 | 5V | 40 |
AT89C1051 | 1K | 64 | 15 | 1 | 3 | 3V | 20 |
AT89C2051 | 2K | 128 | 32 | 3 | 8 | 3V | 20 |
AT89LV51 | 4K | 128 | 32 | 2 | 6 | 3V | 40 |
AT89LV52 | 8K | 128 | 32 | 3 | 8 | 3V | 40 |
DS5000 from Dallas Semiconductor
Dallas Semiconductor fabricated the NV-RAM version of the 8051 which is known as DS5000. The PC serial port is utilized to load the program onto the in-built ROM. The advantage of NV-RAM memory is the facility to erase the contents one byte at a time.
One - Time - Programmable (OTP) versions of the 8051
This version of microcontroller is cheaper and available from various manufacturers. The manufacturers use OTP microcontroller for mass production because the price per unit is very cheap.
Features of 8051
The main features of 8051 microcontroller are:
v RAM – 128 Bytes (Data memory)
v ROM – 4 Kbytes (ROM signify the on – chip program space)
v Serial Port – Using UART makes it simpler to interface for serial communication.
v Input/output Pins – 4 Ports of 8 bits each on a single chip.
v 8 – bit ALU (Arithmetic Logic Unit)
v Harvard Memory Architecture – It has 16 bit Address bus (each of RAM and ROM) and 8 bit Data Bus.
v 8051 can execute 1 million one-cycle instructions per second with a clock frequency of 12MHz.
Memory Architecture
The 4 discrete types of memory in 8051 are:
Internal RAM
This memory is located from address 0 to 0xff. The memory locations from 0x00 to 0x7F are accessed directly. The bytes from 0x20 to 0x2F are bit-addressable. Loading R0 and R1 the memory location from 0x80 to 0xFF can easily accessed.
Special Function Registers (SFR)
Located from address 0x80 to 0xFF of the memory location. The same instructions used for lower half of Internal RAM can be used to access SFR’s. The SFR’s are bit addressable too.
Program Memory
This is read only memory which is located at address 0. With the help of 16 bit Special Function Register DPTR, this memory can also save the tables of constants.
External Data Memory
Located at address 0. The Instruction MOVX (Move External) should be used to access the external data memory.
Application
The 8051 has been in use in a wide number of devices, mainly because it is easy to integrate into a project or build a device around. The following are the main areas of focus: Energy Management:
Efficient metering systems help in controlling energy usage in homes and industrial applications. These metering systems are made capable by incorporating microcontrollers.
touch screens:
A high number of microcontroller providers incorporate touch-sensing capabilities in their designs. Portable electronics such as cell phones, media players and gaming devices are examples of microcontroller-based touch screens.
A automobiles:
The 8051 finds wide acceptance in providing automobile solutions. They are widely used in hybrid vehicles to manage engine variants. Additionally, functions such as cruise control and anti-brake system have been made more efficient with the use of microcontrollers.
Medical Devices:
Portable medical devices such as blood pressure and glucose monitors use microcontrollers will to display data, thus providing higher reliability in providing medical results.
Source credit : Wikipedia, Engineersgarage
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