The difference between AT89C51 and AT89S51/52

Here, beginners need to clarify a product concept in the actual use of microcontrollers. The MCS-51 microcontroller was launched by the American INTE company in 1980. Typical products include 8031 ​​(no internal program memory, and 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, microcontrollers compatible with the MCS-51 core series are still the mainstream products used (such as the currently popular 89S51, 89C51, etc.), and the training materials of various universities and professional schools still use the MCS-51 microcontroller as a representative for theoretical basic learning.

The new features of AT89S51 compared to AT89C51 include:

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

-- ISP online programming function. The advantage of this function is that it does not need to remove the chip from the working environment to rewrite the program in the microcontroller memory. 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.

-- Has a duplex UART serial channel.

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

-- Dual data indicator.

-- Power off indicator.

-- Brand-new encryption algorithm makes it impossible to decrypt 89S51, greatly enhancing the confidentiality of the program, thus effectively protecting intellectual property rights from infringement.

-- Compatibility: Fully backward compatible with all 51-bit products. For example, 8051, 89C51 and other early MCS-51 compatible products. In other words, all programs in textbooks and online tutorials (regardless of whether the microcontroller used in the textbook is 8051, 89C51 or MCS-51, etc.) can run normally on 89S51. This is the so-called backward compatibility.

AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller. It contains 8k Bytes ISP (In-system programmable) Flash read-only program memory that can be repeatedly erased and written 1000 times. The device is manufactured using ATMEL's high-density, non-volatile storage technology and is compatible with the standard MCS-51 instruction system and 80C51 pin structure. The chip integrates a general-purpose 8-bit central processing unit and ISP Flash storage unit. The powerful microcomputer AT89S51 can provide cost-effective solutions for many embedded control application systems.

AT89S51 has the following features: 40 pins, 8k Bytes Flash on-chip program memory, 128 bytes of random access data memory (RAM), 32 external bidirectional input/output (I/O) ports, 5 interrupt priority levels, 2 levels of nested interrupts, 2 16-bit programmable timers and counters, 2 full-duplex serial communication ports, watchdog (WDT) circuit, and on-chip clock oscillator.

In addition, AT89S52 is designed and configured with an oscillation frequency of 0Hz and a power saving mode that can be set by software. In idle mode, the CPU suspends work, while the RAM timer counter, serial port, and external interrupt system continue to work. The power-down mode freezes the oscillator and saves the RAM data, stopping other chip functions until the external interrupt is activated or the hardware is reset. At the same time, the chip also has three packaging forms such as PDIP, TQFP and PLCC to meet the needs of different products.

Compared with AT89C51, AT89S51 has the same appearance and pins. The HEX program of AT89C51 can be directly run on AT89S51 without any conversion, and the results are the same. AT89S has some new functions compared with AT89C51, and the main features are support for online programming and watchdog.

The main differences between them are as follows:

1. Pin function: The pins are almost the same, the only difference is that in AT89S51, P1.5, P1.6, and P1.7 have a second function, that is, the second function of these three pins constitutes the serial ISP programming interface.

2. Programming function: AT89C51 only supports parallel programming, while AT89S51 not only supports parallel programming but also supports ISP re-programming. In terms of programming voltage, in addition to the normal working 5V, the programming voltage of AT89C51 requires 12V Vpp, while AT89S51 only needs 4-5V.

3. Higher number of programming times: The nominal programming times of AT89S51 is 1000 times, but the actual number is 1000-10000 times, which is more conducive to repeated programming for beginners and reduces learning costs.

4. Higher operating frequency: The maximum operating frequency of AT89C51 is 24MHZ, while the maximum operating frequency of AT89S51 is 33MHZ (AT89S51 chip has two models, supporting maximum operating frequencies of 24MHZ and 33MHZ respectively), thus having faster computing speed.

5. Wider power supply range: AT89S51 has an operating voltage range of 4-5.5V, while AT89C51 cannot work properly when the voltage is lower than 4.8V or higher than 5.3V.

6. Stronger anti-interference ability: AT89S51 has an internal integrated watchdog timer, while AT89C51 requires an external watchdog timer circuit, or uses the internal timer of the microcontroller to form a software watchdog to achieve software anti-interference.

7: Stronger encryption function: AT89S51 series provides three-layer encryption algorithm (LB1, LB2, LB3 three programmable encryption bits), which makes decryption of AT89S51 almost impossible and greatly enhances the confidentiality of the program.

8: AT89S51 has newly added SFR and dual data pointers. AT89S51 is fully backward compatible with all products in the 51 series and has a higher cost-performance ratio. Beginners should choose this type of microcontroller to learn as much as possible.

The difference between 89s51 and 89s52

Except that 89S51/52 has ISP download line and watchdog, the difference should be the same as 89C51/52

89S51: 4KROM, 128RAM, 4 interrupt sources, 2 timers

89S52: 8K ROM, 256 RAM, 5 interrupt sources, 3 timers (the additional timer compared to 51 has capture function)