In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051. This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one serial port, and four ports (each 8-bits wide) all on a single chip. At the time it was also referred to as a “system on a chip”. The 8051 is an 8-bit processor, meaning that the CPU can work on only 8 bits of data at a time. Data larger than 8 bits has to be broken into 8-bit pieces to be processed by the CPU. The 8051 has a total of four 1/O ports, each 8 bits wide. Although the 8051 can have a maximum of 64K bytes of on-chip ROM, many manufacturers have put only 4K bytes on the chip.
The 8051 became widely popular after Intel allowed other manufacturers to make and market any flavor of the 8051 they please with the condition that they remain code-compatible with the 8051. This has led to many versions of the 8051 with different speeds and amounts of on-chip ROM marketed by more than half a dozen manufactures. It is important to note that although there are different flavors of the 8051 in terms of speed and mount of on – chip ROM, they are all compatible with the original 8051 as far as the instructions are concerned.
The following link was also given in the last post;
http://www.atmel.com/dyn/products/devices.asp?family_id=604
Now here you can see a lot number of MCU. I will describe them one by one so that the chioce can be made easy.
1-CAN Networking MCUs; CAN stands for "Control Area Network". These MCU have built-in error-detection and error-correction capabilities. Using serial Communication MCU is connected to the Network. These MCU are used for industrial purposes for automotive engine control communication in cars and buses. Similarly it is used in Automotive industry for different manufacturing processes, in avionics, in elevators and automatic doors.
So, its enough powerful. But certainly its a not good thing to start for beginners.
2-Flash (Reprogrammable) MCUs; The flash microcontrollers can be re-programmed after they are shipped. Data written to flash memory can be electrically erased, allowing new data to be written. For older types of flash memory, which use two power supplies (in addition to the power supply for VDD, a separate power supply is provided for VPP for programming), the program can be overwritten by using a dedicated flash programme. More recent types of flash memory are single power supply versions (which do not need a separate power supply for programming). Besides dedicated flash programmers, there are also other ways to program/reprogram and write new data to these devices. Also, among the microcontrollers with single power supply type flash memory that can be programmed after shipment, there are some in which part of the flash memory used to store data instead of an EEPROM. Thus, flash microcontrollers can serve a wide range of applications. more product families that use only flash memory and no longer include mask ROM.These MCU includes AT89CX family MCUs which we will use in our circuits. The detail of these and other MCU can be obtained from the address given below;
http://www.atmel.com/dyn/products/param_table.asp?family_id=604&OrderBy=part_no&Direction=ASC
If you go to the this link you can see the AT89CX family based MCUs including MCU from AT89C2051 to AT89S8253. You can use use AT89C51 MCU which is not given in the list or you can use AT89LS51/52 and AT89S51/52 from the list.
3-Flash ISP (In-System Programmable); These MCU are based on the 8051 architecture.
These MCU have the non-volatile memory (means that memory will not be washed away when the power is Off), The On-chip ISP Flash allows the Program memory to be re-programmed In-System through an SPI serial interface The on-chip FLASH memory can be programmed by byte or by block, either in parallel or in serial mode. We can use these MCU where we need to program the memory during system is running and we want to program the MCUs without removing them from the system, but certainly we are not at this level and also these MCUs are expensive.
4-Flash ISP - Single Cycle Core; For a CPU to execute an instruction takes a certain number of clock cycle. in 8051 family these clock cycles are referred to as machine cycles. THis length of machine cycle depends upon the frequency of the oscillator which we will discuss in our later posts. The 8051 CPU requires 12 clock cycles to execute a single instruction. But this family of MCU consists of high performance 8-bit microcontrollers that execute most instructions in
a single clock cycle, which certainly reduces the delay in executing the instructions. You can say these MCUs are 12 times more faster than traditional 8051 MCU. These MCU are used in battery management, universal remotre control and in industrial and motor control
5- Lightning MCU; These MCU are dedicated to Lightning control. These are not used in common applications.Application include street lightning, lightning for marriages, high intensity flourscent lamps, etc.
6-OTP (One-Time Programmable); As the name suggests, these MCU are only one time programmable, means once they are programmed they cannot be programmaed again. These MCU are used in industrial purposes and for manufacturing where the products are made and the MCU used need not to be programmed again and again. EPROM is similar to OTP memory which can be cleared or deleted using UV(Ultra Violet) rays which a user cannot, but the difference is in their packaging. But in our case we need to reprogram a MCU so these cannot be used.
7- With and Without ROM; You can understand from name that these MCU have either ROM or they are without ROM. Mask ROM versions are semi-custom products in which user programs are written to this ROM before the product is shipped.ROMless versions connect to external ROMs that are programmed for various applications. These MCUs are designed for systems that can switch among various external and replaceable ROMs, such as for testing, evaluation, etc.
8-USB MCUs; Instead of serial and parallel communication, today USB has got more popularity due to increase in data rate and ease of connecting more devices on a single port. Data transferred to the microcontroller of a device from a serial peripheral interface (SPI) can be sent directly to the PC through a USB connection.
Atmel Product Guide;
www.partsearch.ru/_files/ATMEL_GUIDE.pdf
Find the MCU according to your need;
http://www.keil.com/dd/search_parm.asp
Different questions regarding type of MCU;
http://www.necel.com/en/faq/mi_com/__com_kind.html
http://www.geocities.com/shahzadahmadmalik/guide.html
About Atmel; Founded in 1984, Atmel Corporation is headquartered in San Jose, California San Jose is the third-lar 1-(800) 292-8635. Internationally from a fax phone, dial 1-(408) 441-0732. Requests may be sent via e-mail to literature@atmel.com or by visiting Atmel's website at www.atmel.com.
Atmel Wireless & Microcontrollers Division product information may be retrieved at www.atmel-wm.com.
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