The embedded system is an application system that contains at least one programmable computer (usually a microcontroller, microprocessor or digital signal processing chip) and people who use the system generally not realized that the system is based on a computer.
1. 8052 pieces of RAM are 256 bytes, while 8051 is 128 bytes; more than 8052 more timers (Timer2)
2. Almost, the chips are based on 8052 architectures.
3. SAMLL 8051 does not support the external storage, and Extended 8051 supports large-capacity-in-one storage.
4.Reset pin level is logic 1 and keeps two or more machine cycles, the microcontroller will reset
5. RXD, TXD is used to receive and send serial data INT0 INT0 that uses the RS-232 protocol, INT1 is used to process interrupt input.
6. XTL2, XTL1 is used to connect external oscillator modules
7. VSS is grounded, VCC is a power supply tube foot (5V chip 5V voltage, 3V chip 3V voltage)
8. All computers are driven by some form of oscillator circuits, and the oscillator circuit is the "heartbeat" of the system. The general principle is that the speed of the application run is directly determined by the frequency of the oscillator. In the earliest Intel's 8051 microcontroller, the execution of a machine instruction requires at least 12 oscillator cycles. The earliest 8051 chip maximum oscillator frequency is 12MHz, so peak performance is 1MIP. Obviously, in order to get the greatest performance, we want to perform a machine instruction in an oscillator cycle.
One way to improve 8051 performance is to change the internal structure of the microcontroller, so that the number of oscillation cycles spent each machine instruction is reduced, another method is to increase clock frequency, such as 33MHz (rather than 12MHz)
However, the power supply current and the oscillator frequency are approximately related to the current relationship, and the electromagnetic interference (EMI) generated by the circuit is produced as the clock frequency increases.
9. Desktop machine, when the program is running, the program code often copies from the disk to the RAM, and most embedded systems, the program is implemented in the ROM "
10. From the underlying angle, the interrupt is a hardware mechanism that informs the processor's event; from the upper layer, interrupt is to build multi-task applications to provide a mechanism: the application is to use the same processor simultaneously A task
The timer of 11.8051 is the timer 0 and the timer 1, and there are still a timer 2, which are all 16-bit timers, that is, they can only retain the number between 0 and 65535. This timer is very important for embedded system development. To know that when the setting is accurate, the timer is growing periodically: especially, in most 8051 chips, the timer grows once every 12 oscillatory cycles. We can use it to generate rule time unit "Tick" to drive the operating system, or to determine the function of the function.
12. Most 8051 chips have 4 8-bit ports, and 32 pipes provide you can separately read data or control separately, so ports are two-way, that is, can be used as input. When the standard 8051 system-ground chip is used with external memory, the port 1 is uniquely used to perform a generally I / O operational port.
13. The standard 8051 series chip is a 16-bit address space 8-bit microcontroller. The so-called 8-bit value is the size of the register or data bus. It means that the processing of 8-bit data is relatively fast, and the efficiency of the 16-bit or 32-bit data is very low; the 16-bit address space means that the chip can directly address 2 16-byte memory, of course, to achieve these limits, Need to connect the memory to the peripheral interface
