The STC51 has a program-cured procedure, which the role of this program is to detect whether the serial port is downloading the program, and does not need to perform the user program in the microcontroller. Run this program at a time, this is why you want to start cold every time you download. After the reset, the microcontroller is executed from the address 0x0000H, and the address 0x0000h will point to the main function entry, the main function, that is, the user program that is downloaded without performing the previously cured detection serial port. That's why the single-chip microcomputer is downloaded coldly, and the reset is not. Note that the macro defined in front of the program does not occupy the system time, so the main program is the main function.
There is a way to give users who need to power up immediately, the STC microcontroller can set only P1.0 / P1.1 when Plus P1.0 / P1.1 begins to download the program at low levels, otherwise the user program is executed directly. This approach is fast, there is no such time to detect the serial port. STC51 single-chip cooling is a must and the reset circuit is not necessary, whether it is cold start or manual startup. That is, I want to download the program to be cold, and there is no reset circuit doesn't matter. However, there must be a reset circuit on the minimum system board, whether it is a power-on reset, or a power-on plus manual reset, although it does not see the difference in some simple programs, but because the reset operation will affect some special registers, there is no reset An error occurs when the function is executed again. After the single-chip offline is electrically connected, it will continue to be executed from the main function. It may be that the single-chip offline is automatically returned to 0x0000H, but the values in the special registers will not change.
The power-up reset and manual reset of the single chip microcomputer is a relatively simple circuit, as long as it is based on the reset time TRESET required by the single-chip manual, it is less than the RC constant in the reset circuit.
Single chip microcomputer downloads are generally through serial ports, that is, the on-site communication of the host machine (STC-ISP) and the underlying communication of the microcontroller are implemented through the serial protocol, and the more advanced communication protocols between the two are built on the serial protocol.
Note2: The upper machine (STC-ISP) detects the timing of single-chip microcomputer
The baud rate is a time occupied by the serial port, which is 2400, that is, the time occupied by each bit is 1/2400 = 4.167 * e-4 (s); can click to detect the MCU option, the host computer starts with Single chip shake hands. The whole handshake process can be obtained from Figure 2.2, and orange is inquiry pulse transmitted by the upper computer, the blue-collected machine response pulse, technology area
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