The PIC microcontroller series is a product of Microship in the United States. It is divided into three levels, namely basic, intermediate, and advanced. It is one of the fastest-growing microcontrollers in the current market share. The CPU adopts a RISC structure and has 33 and 35 , 58 instructions are a streamlined instruction set. At the same time, it adopts the Harvard dual-bus structure, which runs fast. It can make program memory access and data memory access parallel processing. This instruction pipeline structure completes two parts of work in one cycle One is to execute the instruction, and the other is to fetch the next instruction from the program memory. In general, each instruction only needs one cycle. This is also one of the reasons for the efficient operation. In addition, the reason why the PIC microcontroller has become a very hot microcontroller for a while It is nothing more than the following features:
1. It has the characteristics of low working voltage, low power consumption and strong driving ability. The I/O port of the PIC series single-chip microcomputer is bidirectional, and its output circuit is a CMOS complementary push-pull output circuit. The I/O pin adds a direction register for setting the input or output state, which solves the problem that the 51 series I/O pin is both input and output when it is high.
2. When set to 1, it is in the input state, and no matter whether the pin is high or low, it is in a high impedance state; when it is set to 0, it is in the output state, no matter what level the pin is, it is in low In resistance state, it has considerable drive capability, low-level sink current up to 25mA, high-level output current up to 20mA. Compared to the 51 series, this is a big advantage
3. It can directly drive the digital tube display and the external circuit is simple. Its A/D is 10 bits, which can meet the accuracy requirements. With online debugging and programming (ISP) function.
ShortcomingsIts special registers (SFR) are not all concentrated in a fixed address range (80-FFH) like the 51 series, but are scattered in four address ranges. There are only 5 special registers PCL, STATUS, FSR, PCLATH, INTCON appear in the 4 memory banks at the same time, but in the programming process, it is necessary to deal with the special registers, you have to repeatedly select the corresponding memory bank, that is, the status register STATUS The 6th bit (RP1) and 5th bit (RP0) are set or cleared. Basically, data transmission and logic operations must be carried out through the working register W (equivalent to the accumulator A of the 51 series), and the 51 series can also be directly transmitted to each other through the register, so the bottleneck phenomenon of the PIC microcontroller is higher than that of the 51 series Even more serious, this friend in programming should have a deep understanding.
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