51 single chip microcomputer scheme is a general term for single chip microcomputer compatible with Intel 8051 instruction system. 51 single chip microcomputer is widely used in household appliances, automobiles, industrial measurement and control and communication equipment. Because the instruction system and internal structure of 51 single chip microcomputer are relatively simple, many domestic colleges and universities use it for introduction teaching of single chip microcomputer.

The same program runs on the hardware of each single chip microcomputer manufacturer with the same results, such as ATMEL's 89C51 (discontinued), 89S51, Philips, Winbond, etc. we often say that the discontinued 89C51 refers to ATMEL's AT89C51 single chip microcomputer. At the same time, it enhances many features on the original basis, such as clock, What's more, flash (the content of program memory can be rewritten at least 1000 times) memory replaces the original ROM (one-time write). The performance of AT89C51 is very superior to 8051. The new functions of 89S51 relative to 89C51 include:

--Many new functions have been added, the performance has been greatly improved, and the price is basically the same, even lower than 89C51.

--ISP online programming function, the advantage of this function is to rewrite the program in the MCU memory without stripping the chip from the working environment. Is a powerful and easy-to-use function.

--The high working frequency is 33MHz. As we all know, the limit working frequency of 89C51 is 24m, that is, s51 has a higher working frequency, so it has a faster calculation speed.

--With duplex UART serial channel.

--The internal integrated watchdog timer no longer needs an external watchdog timer unit circuit like 89C51.

--Dual data indicator.

--Power off identification.

--The new encryption algorithm makes the piracy of 89S51 impossible, and the confidentiality of the program is greatly strengthened, which can effectively protect intellectual property rights from infringement.

--Compatibility: fully compatible with all 51 word series products. For example, 8051, 89C51 and other early MCS-51 compatible products. In other words, all the programs in textbooks and network tutorials (whether the MCU used in textbooks is 8051 or 89C51 or MCS-51, etc.) can run as usual on 89S51, which is the so-called downward compatibility.