Section 3: Internal structure of PIC16C5X series microcontroller

The PIC16C5X integrates an 8-bit arithmetic logic unit (ALU) and working register (W) on one chip; 384 to 2K of 12-bit program memory (ROM); 32 to 80 8-bit data registers (RAM); 12 to 20 I/O ports; 8-bit counter and prescaler ; clock, reset, and watchdog counter, etc. The internal structure is shown in Figure 1.2:

    As can be seen from the figure, PIC16C5X has a feature that the data memory RAM is used as a register for addressing to facilitate programming. The register group is divided into two parts according to function, namely the special register group and the general register group. The special register group includes the real-time clock counter RTCC , the program counter PC, the status register Status, the I/O port register and the storage bank select register FSR. These registers will be discussed in detail later.

    The PIC bus structure adopts the Harvard structure with independent separation of data line (8 bits) and instruction line (12 bits). This can improve the instruction speed of the microcontroller . When an instruction is executed in the ALU, the next instruction has been taken out and placed in the instruction register waiting to be executed. The arithmetic logic unit ALU and the working register (W) are responsible for arithmetic and logical operations.

    PIC16C5X provides a two-level stack, so subroutine calls only have two levels. Be sure to pay attention to this when using it, otherwise the program will run out of control.