The origin of S51 and its difference from C51

AT89 Many netizens who are new to 51 microcontrollers will have such questions: What is AT89S51? Books and online tutorials are all about 8051, 89C51, etc.! I have never heard of 89S51. Here, beginners need to clarify a product concept in the actual use of microcontrollers. MCS-51 microcontrollers are products launched by INTEL in the United States in 1980. Typical products include 8031 ​​(no program memory inside, which has been eliminated by the market in actual use), 8051 (the chip uses HMOS, the power consumption is 630mW, which is 5 times that of 89C51, which has been eliminated by the market in actual use) and 8751 and other general products. Until now, the microcontrollers compatible with the MCS-51 core series are still the mainstream products used (such as the currently popular 89S51, the discontinued 89C51, etc.). The training materials of various universities and professional schools still use MCS-51 microcontrollers as representatives for theoretical basic learning.

Some documents even refer to 8051 as the MCS-51 series of single-chip microcomputers. 8051 is the most typical representative work in the early days. Due to the far-reaching influence of MCS-51 single-chip microcomputers, many companies have launched compatible series of single-chip microcomputers, that is, the MCS-51 core has actually become a standard for 8-bit single-chip microcomputers. The 51 single-chip microcomputer products of other companies are all compatible with the MCS-51 core. The same program will have the same results when running on the hardware of various single-chip microcomputer manufacturers, such as ATMEL's 89C51 (discontinued), 89S51, PHILIPS, and WINBOND. The 89C51 that we often say has been discontinued refers to ATMEL's AT89C51 single-chip microcomputer, which has enhanced many features on the original basis, such as the clock. What's more, the original ROM (one-time write) is taken from the Flash (the content of the program memory can be rewritten at least 1,000 times) memory. The performance of AT89C51 is already very superior to 8051. However, in terms of marketization, 89C51 has been challenged by the PIC microcontroller camp. The most fatal flaw of 89C51 is that it does not support the ISP (online update program) function. New functions such as ISP function must be added to better continue the legend of MCS-51. 89S51 replaced 89C51 in this context. Now, 89S51 has become the new darling of the actual application market. Atmel, which has the largest market share, has stopped producing AT89C51 and will replace it with AT89S51. 89S51 has been improved in process. 89S51 adopts 0.35 new process, which reduces costs and improves functions, increasing competitiveness. 89SXX can be compatible with 89CXX and other 51 series chips. At the same time, Atmel no longer accepts orders for 89CXX. The 89C51 that everyone sees in the market is actually a huge inventory produced by Atmel in the early stage. If the market needs it, Atmel can of course resume production of AT89C51.

Compared with 89C51, 89S51 has the following new features:
-- Many new features, greatly improved performance, and only slightly higher price than 89C51
-- ISP online programming function. The advantage of this function is that the program in the microcontroller memory can be rewritten without removing the chip from the working environment. It is a powerful and easy-to-use function.
-- The maximum operating frequency is 33MHz. As we all know, the maximum operating frequency of 89C51 is 24M, which means that S51 has a higher operating frequency and thus a faster computing speed.
-- It has a duplex UART serial channel.
-- Internally integrated watchdog timer, no longer needing an external watchdog timer unit circuit like 89C51.
-- Dual data indicator.
-- Power off mark.
-- Brand-new encryption algorithm, which makes it impossible to decrypt 89S51, and the confidentiality of the program is greatly enhanced, so that intellectual property rights can be effectively protected from infringement.
-- Compatibility: fully backward compatible with all 51-word series products. For example, 8051, 89C51 and other early MCS-51 compatible products. That is to say, all the programs in textbooks and online tutorials (regardless of whether the microcontroller used in the textbook is 8051, 89C51, MCS-51, etc.) can run normally on 89S51. This is the so-called backward compatibility.
Comparison results: Just like the upgrade from INTEL's P3 to P4, although both can run Windows, the speed is different.
The same is true for upgrading from AT89C51 to AT89S51. Compared with S51, C51 is inferior. The technological progress in the actual application market is always moving forward.

A product concept in the actual use of microcontrollers, microcontrollers, 8051 is the most typical representative in the early days, because microcontroller products are all compatible with the MCS-51 core. Challenges of the microcontroller camp, the program in the microcontroller memory does not need to remove the chip from the working environment. It is a powerful and easy-to-use function.