The working principle of ISP

The implementation of ISP is relatively simple. The general method is that the internal memory can be rewritten by the software of the host computer through the serial port. For a single-chip microcomputer, the data from the host computer can be received through SPI or other serial interfaces and written into the memory. So even if we weld the chip to the circuit board, as long as the serial port is left to interface with the host computer, the internal memory of the chip can be rewritten without removing the chip.

Advantages of ISP

The advantage of ISP technology is that it can carry out experiments and development of microcontrollers without a programmer. The microcontroller chip can be directly welded to the circuit board, and the finished product is ready after debugging. , eliminating the inconvenience caused to the chip and circuit board due to frequent insertion and removal of chips during debugging.

There are three ways to implement in-system programming:

1. EEPROM or Flash technology (such as CPLD) based on electrically erasable memory cells. The characteristic is that data will not be lost when power is turned off. , but the number of programming times is limited and the programming speed is slow;

2. The programming unit (such as FPGA) based on SRAM lookup table is characterized by unlimited number of configurations, and the logic can be changed at any time after power-on, but the data after power-off That is, it is lost and needs to be reconfigured next time it is powered on;

3. Based on anti-fuse programming unit (such as Actel's FPGA);