8051 Family
The 8051 family is a popular, industry standard 8-bit single chip micro- computer (microcontroller) family, manufactured by various companies with many different capabilities. The basic standard device, which is the first member of the family, is the 8051, which is a 40-pin microcontroller. This basic device is now available in several configurations. The 80C51 is the low- power CMOS version of the family. The 8751 contains EPROM program memory, used mainly during development work. The 89C51 contains flash programmable and erasable memory (PEROM) where the program memory can be reprogrammed without erasing the chip with ultraviolet light. The 8052 is an enhanced member of the family which contains more RAM and also more timer/counters. There are many versions of the 40-pin family which contain on- chip analogue-to-digital converters, pulse-width modulators, and so on. At the lower end of the 8051 family we have the 20-pin microcontrollers which are code compatible with the 40-pin devices. The 20-pin devices have been manufactured for less complex applications where the I/O requirements are not very high and where less power is required (e.g. in portable applications). The AT89C1051 and AT89C2051 (manufactured by Atmel) are such micro- controllers, which are fully code compatible with the 8051 family and offer reduced power and less functionality. Table 1.1 gives a list of the characteristics of some members of the 8051 family.
In this book all the projects are based upon the AT89C2051 microcontroller. The code given will run on other members of the family, including the 40-pin devices. The reasons for choosing the AT89C2051 are its low cost, low power consumption, small space (20 pin), and powerful features.
In this chapter we shall be looking at the features of the 8051 family briefly with more emphasis on the smaller AT89C2051. More information on these microcontrollers can be obtained from the manufacturers’ data sheets.