AT89S51/52 serial port download cable production process

   See the attached figure for the circuit using ISP online programming. The entire circuit can be built with a multi-purpose board, using the PC's serial port for data communication. The microcontroller programming pins are ⑥ to ⑨. Since the AT89S51/52 ⑨ pin is the reset terminal, this board can only be used as a programming board according to the connection method shown in the figure. If this board is to be able to run, a "programming" and "running" switch must be added to the ⑨ pin. In the "running" state, the ⑨ pin must be connected to a conventional RC reset circuit. When "programming", the ⑨ pin is changed to the +5V power supply terminal to increase the voltage to the high level required for programming.

   If the programmer needs to work stably, 74HC244 can be added between MAX232 and AT89S51 as a drive buffer. However, in most cases, the circuit shown in the attached figure can meet the requirements.
 

   The software is called "Electronic Online ISP Programmer V2.0". It can be downloaded anywhere on the Internet and uses the WINDOWS operation interface, which is easy to use. The specific usage is as follows:

   First open the software interface, then open the programmer. Under the condition that the serial line (parallel lines, not cross lines) is connected reliably, click "ID Identification" in the software, and the chip model will appear in the dialog box: AT89S51 or AT89S52. Click "Erase", and a progress bar will flash in the lower right corner, and a dialogue will appear: Erase completed. At this time, click "ID Identification" again. If the prompt "Line is blocked or chip cannot be identified" appears, you should restart the programmer once and click "ID Identification" again. After the model is successfully displayed, click the "File" drop-down menu to "Load Hex File", select the pre-compiled hexadecimal file on the computer, double-click the file name, and the file name will appear in the dialog box. It means that it has been selected. Finally, click "Write", and the write operation can be completed quickly. A "marquee" program can be written in about 0.8 seconds, which is very convenient.

    Remember: Every time you perform chip operations, such as writing, erasing, and verifying, you must perform "ID authentication" to check stability.

   Description: 1. The microcontroller can be made into a complete system board, designed to switch programming/operation.

   2. Pin 9 of AT89S51/52 is the reset pin. In the ISP online programming mode, it must be connected to the high level Vcc:, that is, the power supply voltage +5V.

   3. The matching software can be downloaded for free on the Internet. There are many addresses. You can search for relevant resources on your own.

   4. This circuit is not stable. For different operations, such as clearing and erasing, programming and writing chips, it is easy to drop the line when switching operations. At this time, you only need to turn the power supply of the circuit on and off again. In addition, before each operation, you should use the software "identification" function to verify whether the line is unobstructed.

   The programmer described in this article is only suitable for Atmel's AT89S51 and AT89S52 microcontrollers. The AT89S microcontroller series supports ISP online programming function. This function greatly reduces the workload of microcontroller development and there is no need to purchase a dedicated programmer. Therefore, it is very suitable for enthusiasts to practice microcontroller development and can also be used as a reference for relevant engineering and technical personnel.