1, an 8-bit microprocessor CPU.
2, in-chip data memory (RAM128B / 256B): to store data that can be read / written, such as intermediate results, end results, and data to display.
3, in-chip 4KB program memory Flash ROM (4KB): to store programs, some raw data, and tables.
5, two or three timing / counters: Each timing / counter can be set to a counting method to count the external event, or set to time, and can implement computer control depending on the count or timing.
6, a serial I / O port of a full-duplex UART: a single-chip communication between a single-chip microcomputer or other microcomputer can be realized.
7, in-chip oscillator and clock generation circuit: but need to pass crystallization and capacitance.
8, the interrupt control system for five interrupt sources.
9, with power saving mode: leisure mode and power-down mode.
In idle mode, the CPU stops working, while RAM, Timer / Counters, serial ports, and interrupt systems continue. The current at this time can be reduced to 15% of the normal operating mode. In the power-down mode, the in-chip oscillator stops working, because the clock is "freezed", so that all functions are paused, so only the contents in the film in the film are saved until the next hardware reset. The current in this manner can be reduced to 15 μA, minimum can be minimized to 06 μA.
structure:
It consists of a central processing unit (CPU), a memory (ROM, and RAM), and I / O interface. The internal structure of the 89C51 single-chip microcomputer is shown in the figure:
The following is MCS-51
MCS-51 configuration features of single-chip memory
1 Internal integration of 4K program memory ROM;
2 There is 256B data memory RAM inside;
3 You can take an external 64K program memory ROM and data memory RAM.
From the perspective of physical structure, the 51 single-chip storage system can be divided into four storage space: both the Sub-filled ROM, RAM, and the film ROM, RAM.
From logically (both programmed angles), 51 single-chip storage systems are actually divided into three storage spaces.
1. On-chip data memory RAM;
2. Amount data memory RAM;
3. The program memory ROM (determined by the EA level) in the interior or outside.
1. Program memory ROM is used to store programs, constants, or forms.
2. In the 51 single-chip microcomputer, in the level of the pin / EA, when ROM: EA = 1, the CPU performs a program in the 4krom in the film; EA = 0, the CPU selection procedure outside the ROM .
3. Whether it is in the slice or using a slice of ROM, the start address of the program starts from the 0000H unit of the ROM.
4. Although the system can be provided at the same time with the internal ROM and external ROM, it is selected to select one (or use the internal ROM, or using an external ROM) by the setting of / EA, or using an external ROM.
5. If EA = 1 (when the program is executed in the on-chip program memory): If the plugager PC value exceeds 0FFFH (4K), the microcontroller is to automatically turn the ROM memory outside the sheet and start executing the program from the 1000H unit ( Unable to use the low 4K space of the film outside).
6. When the program exceeds 4K, there are two ways to use the program memory ROM:
1 Set EA = 0, use the external ROM. Starting from the address = 0000h;
2 Set EA = 1, use the internal 4kROM and external ROM (the unit starting from 1000 hours).
Six special units of program memory:
Six units in the ROM have specific functions.
0000H unit: The unit pointed to by the program counter PC when reset, so it is used to store the first instruction in the program;
0003H Unit: Vector inlet address of external interrupt / INT0;
000BH unit: The vector entry address of the timer T0 overflows the interrupt;
0013H unit: vector inlet address of external interrupt / INT1;
001BH unit: The overflow interrupt vector inlet address of the timer T1;
0023H Unit: The serial port is received, the transmitted interrupt vector inlet address is transmitted.
Vector Entry Unit: When writing interrupt programs, write the corresponding "Springboard Directive"
Two characteristics of the first instruction of the single chip microcontroller:
1 Store 0000H unit of the ROM;
2 must be "Jump Directive" to skip the 5 interrupt vectors below to go to the real main program entry 0100h unit.
ORG 0000H LJMP 0100H
ORG 0100H
Start: Mov A, # 00H
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End
External program memory:
When a single-chip uses an external ROM memory (extended system), / EA = 0 must be set, at which time the port function of the microcontroller has to change:
1 P0, P2 as the address and data bus of the external ROM;
2 Use pin / PSEN signals to stroll through external ROM data trial output.
Internal Data Memory RAM:
Regardless of physical or logically, RAM can be divided into two independent spaces: internal and external RAM. Access from different instructions.
1. Use the MOV instruction when accessing internal data storage units;
2. Use the MOVX instruction when accessing external data memories. The internal RAM is functionally divided into two different blocks from the function of 256B:
1. Low 128B RAM block;
2. High 128b SFR (Special Function Register) block.
It can be divided in the lower 128B RAM storage unit:
1. Work register;
2. Bit address area;
3. "Tile Zone" of Universal Storage Data.
Only 21 registers (51 series) are only used in the dedicated register zone SFR of the high 128b, and 107 units cannot be used. , Read full text, original title: single-chip structure and principle
Article Source: [Micro Signal: MCU168, WeChat public number: Hardware siege] Welcome to add attention! Please indicate the source of the article.
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