Introduction to the differences and characteristics of various types of 51 single-chip microcomputers

8031/8051/8751 are early products of Intel.

Features of 8031 ​​8031

​​has no internal program memory ROM. When using it, users need to connect an external program memory and a logic circuit 373. The external program memory is mostly EPROM 2764 series. If the user wants to modify the program written in EPROM, he must first use a special ultraviolet lamp to erase it before writing it. The program code written in the external program memory has no confidentiality.

Features of 8051

8051 has 4k ROM inside the chip, and no external memory or 373 is required, which can better reflect the simplicity of "single chip". However, you cannot burn your program into its ROM. You can only hand over the program to the chip manufacturer to burn it for you, and it is a one-time thing. In the future, neither you nor the chip manufacturer can rewrite its content.

Features of 8751

8751 is basically the same as 8051, but 8751 has 4k EPROM inside the chip. Users can write their own programs into the EPROM of the microcontroller for field experiments and applications. The rewriting of EPROM also needs to be erased by ultraviolet light for a certain period of time before burning.

Because the above-mentioned type of microcontroller was applied early and had a great influence, it has become the de facto industrial standard. Later, many chip manufacturers cooperated with Intel in various ways and launched the same type of microcontroller. Just like multiple versions of a single-chip microcomputer, although they are constantly changing the manufacturing process, the core is the same, that is, the instruction system of this type of microcontroller is fully compatible, and most of the pins are also compatible; they can basically be directly interchangeable in use. People collectively call these MCUs with the same core as 8051 "51 series MCUs". For learners, if they learn one of them, they will know all 51 series.

Features of AT89C51 and AT89S51

Among the many 51 series MCUs, ATMEL's AT89C51 and AT89S51 are more practical, because they are not only fully compatible with 8051 instructions and pins, but also the 4K program memory on the chip is FLASH technology. The memory of this technology can be instantly erased and rewritten by users in an electric way. Generally, programmers made specifically for ATMEL AT89xx have these functions. Obviously, this MCU has very low requirements for development equipment and greatly shortens the development time. The program written into the MCU can also be encrypted, which protects your labor results very well. In addition, the current price of AT89C51 and AT89S51 is lower than that of 8031, and the market supply is also sufficient.

AT89S51 and 52 are new products launched by ATMEL in 2003. In addition to being fully compatible with 8051, they also have ISP programming and watchdog functions. We have also designed a programming, learning, and experimental board specifically for this new chip.

Features of AT89C2051, AT89C1051, etc.

ATMEL's 51 series also includes AT89C2051, AT89C1051, etc. These chips are simplified versions of AT89C51 after some functions are simplified. AT89C2051 removes P0 and P2 ports, and the internal program FLASH memory is as small as 2K. The package form is also changed from 51's P40 pin to 20 pin, and the corresponding price is also lower. It is especially suitable for use in some circuit environments with small programs such as smart toys and handheld instruments; AT89C1051 further streamlines the serial port function on the basis of 2051, and the program memory is reduced to 1k again, and of course the price is also lower.

For 2051 and 1051, although some resources are reduced, they both integrate a precision comparator in the chip. Don't underestimate this small comparator, it provides great convenience for us to measure some analog signals. With a few resistors and capacitors , we can measure voltage , temperature and other quantities we need in daily life. This is a very valuable resource for the design of many daily electrical appliances.

ATMEL's 51, 2051, and 1051 all have multiple packages, such as AT89C (S) 51 has P DIP , PLCC and P QFP / TQ FP packages; 2051/1051 has PDIP and SOIC packages. The following figure shows some of the actual packages.

Since the cores of the 51 series microcontrollers are the same, the textbooks for 51 microcontrollers are still based on the books on Intel MCS 8051 microcontrollers. The same is true for development software and tools. We collectively refer to them as 8051 development systems, environments, and so on. For example, the assembler programs ASM51, Keil C51, and MedWin introduced on our website are all development software for 8051 core microcontrollers.

For AT89C51 and AT89S51, 8051\\8751 can be directly interchanged in actual circuits. The only difference in replacing 8031 ​​is the 31st pin. Since 8031 ​​has no internal ROM, the 31st pin needs to be grounded (GND). After the microcontroller is started, it reads instructions from the external program memory; while 8051/8751/89c51 has an internal program memory, and the 31st pin is connected to a high level (V CC ). After the microcontroller is started, it directly reads instructions from the internal. That is, the 31st pin of the 51 chip controls whether the microcontroller program is read from the internal or external. The 31st pin is connected to the power supply , and the program is read from the internal. The 31st pin is grounded, and the program is read from the external. No other changes are required. In addition, after replacing 8031, AT89C51 and AT89s51 do not use external memory, so there is no need to install the external memory and 373 chip of the original circuit.

The difference between 89S51 and 89C51

Many netizens who are new to 51 microcontrollers will have such questions: What is AT89S51? Books and online tutorials all mention 8051, 89C51, etc.! I have never heard of 89S51? !
　
　　Here, beginners need to clarify a product concept in the actual use of single-chip microcomputers. The MCS-51 single-chip microcomputer was launched by the American INTE company in 1980. Typical products include 8031 ​​(no internal program memory, 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, and has been eliminated by the market in actual use) and 8751 and other general products. Until now, the single-chip microcomputers compatible with the MCS-51 core series are still the mainstream products used (such as the currently popular 89S51, 89C51, etc.). The training materials of various universities and professional schools still use the MCS-51 single-chip microcomputer as a representative for theoretical basic learning.

　　Some literature even refers to the MCS-51 series of single-chip microcomputers as 8051. 8051 is the most typical representative work in the early days. Due to the far-reaching influence of the MCS-51 single-chip microcomputer, many companies have launched compatible series of single-chip microcomputers, which means that 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 refer to as the discontinued 89C51 refers to ATMEL's AT89C51 single-chip microcomputer. At the same time, it 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 contents of the program memory can be rewritten at least 1,000 times) memory. The performance of AT89C51 is already very superior to that of 8051.

　　However, in terms of marketization, 89C51 has been influenced by P ICThe challenge of the single-chip microcomputer camp, the most fatal flaw of 89C51 is that it does not support ISP (online update program) function, and 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 cost and improves function, 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 the huge inventory produced by Atmel in the early stage. If the market needs it, Atmel can of course resume production of AT89C51.

The new features added by 89S51 compared with 89C51 include:

-- Many new features have been added, the performance has been greatly improved, and the price remains basically unchanged, even lower than 89C51!

-- ISP online programming function. The advantage of this function is that the program in the microcontroller memory does not need to be removed from the working environment. It is a powerful and easy-to-use function.

-- The highest operating frequency is 33M Hz . As we all know, the maximum operating frequency of 89C51 is 24M, which means that S51 has a higher operating frequency and thus has a faster computing speed.

-- It has a duplex UART serial channel.

-- Internally integrated watchdog timer, no longer need an external watchdog timer unit circuit like 89C51.

-- Dual data indicator.

-- Power off mark.

-- Brand-new encryption algorithm, which makes it impossible to hack into 89S51, and the confidentiality of the program is greatly enhanced, so that intellectual property rights can be effectively protected from infringement.

-- Compatibility: fully 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 98, the speed is different. The upgrade from AT89C51 to AT89S51 is the same. Compared with S51, C51 is inferior. The technological progress in the actual application market is always moving forward.