Intel introduced the MCS-51 family of microcontrollers in 1980 as an enhanced MCS-48. The 8051 is the main processor in this family, featuring 4K EPROM, 128 bytes of RAM, 2x 16-bit timer/counters, serial UART, 2x external active low interrupts that can either be level or edge triggered (falling edge only), RAM stack that can address the full RAM space, vectored interrupts, and 16-bit address/8-bit data front side bus. The 8051 also includes a dedicated address latch pin (ALE), dedicated external program ROM read strobe pin (PSEN), and an active low external access pin (EA). When EA is externally tied high, the 8051 executes code from its internal ROM while addressing instructions past the internal program ROM space addresses external ROM if present. All code execution takes place from external program ROM if EA is tied low.
The 8051's 16-bit program counter and front side bus can address up to 65536 external memory addresses for compatibility with a total of 64K external program ROM space. The 8051 also has a read and write strobe available (P3.6/WR and P3.7/RD) for up to 64K of external RAM as well.
The 8052 is the 8051's big brother. It is identical to the 8051, with the addition of 8KB on chip program ROM, a 3rd 16-bit timer/counter with 16-bit autoreload (this timer can also be used as the baud rate generator for the UART in 16-bit autoreload, making for a baud timer with greater resolution for more available baud rates with just about any crystal), and a capture module that works with timer 2. The 8052 also has an additional 128B of RAM, making for a total of 256 bytes of on chip RAM space. The upper 128 bytes of RAM can only be indirectly addressed.
The AT89S52 is Atmel's derivative of the 8052. It is compatible with Atmel's In-System Programming (ISP) via an on chip SPI interface, which allows it to be programmed via Atmel's AT89ISP programmer while the MCU is in the target circuit.
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89S52 have 8KB ROM and 256bytes RAM also it supports SPI program downloading but 89C51 have 4Kb ROM, 128bytes RAM and it wont support Serial program downloading. For more details visit www.8051projects.info
avr is high speed cmpar to 8051.in 8051 there are less number of instructions
AT89S52 is a microcontroller based on the Intel 8051 architecture and features. Concerning your question, AT89S52 is the heart of most project involving Dual Tone Multi Frequency (DTMF), that is to say it is the controller IC used in such project.
AT - Atmel , 89 - manufacturer's series , S - silicon CMOS , 52 - is the family of 8051 i.e., 8052 MC .
internal and external memory
architecture
89s51 and 89s52 both are same version of 8051 microcontroller
The difference is that those MCUs that start with 80 are romless, those with 87 use EPROM erasable by light
can we replace AT89c51 by AT89s52 but i have c51 code
The Atmel AT89S52 is a microcontroller in the 80C51 family.