单片机英文资料

A microcontroller or MCU is a computer on a chip that is the CPU memory and time counters input output interface are integrated in a piece of integrated circuit chip microcomputer Even though most of his features in a small chip but it has a need to complete the majority of computer components CPU memory internal and external bus system most will have the Core At the same time such as integrated communication interfaces timers real time clock and other peripheral equipment And now the most powerful single chip microcomputer system can even voice image networking input and output complex system integration on a single chip It is a type of microprocessor emphasizing self sufficiency and cost effectiveness in contrast to a general purpose microprocessor the kind used in a PC The majority of computer systems in use today are embedded in other machinery such as telephones clocks appliances vehicles and infrastructure An embedded system usually has minimal requirements for memory and program length and may require simple but unusual input output systems For example most embedded systems lack keyboards screens disks printers or other recognizable I O devices of a personal computer They may control electric motors relays or voltages and read switches variable resistors or other electronic devices Often the only I O device readable by a human is a single light emitting diode and severe cost or power constraints can even eliminate that Due to the development of old microcontroller is very fast already cannot satisfy the definition so in many applications is called a wider range of micro controller but at present in China is still much continue chip Also known as single chip MCU Microcontroller because it was first used in the field of industrial control Only by the single chip CPU chip developed from the dedicated processor The design concept is the first by a large number of peripherals and CPU in a single chip the computer system so that smaller more easily integrated into the complex and demanding on the volume control devices INTEL the Z80 is one of the first design in accordance with the idea of the processor From then on the MCU and the development of a dedicated processor parted ways Early single chip 8 bit or all of the four One of the most successful is INTEL s 8031 because the performance of a simple and reliable access to a lot of good praise Since then in 8031 to develop a single chip microcomputer system MCS51 series Based on single chip microcomputer system of the system is still widely used until now As the field of industrial control requirements increase in the beginning of a 16 bit single chip but not ideal because the price has not been very widely used After the 90 s with the big consumer electronics product development single chip technology is a huge improvement INTEL i960 Series with subsequent ARM in particular a broad range of applications quickly replaced by 32 bit single chip 16 bit single chip high end status and enter the mainstream market Traditional 8 bit single chip performance has been the rapid increase in processing power compared to the 80 s to raise a few hundred times At present the high end 32 bit single chip frequency over 300MHz the performance of the mid 90 s close on the heels of a special processor while the ordinary price of the model dropped to one U S dollars the most high end models only 10 U S dollars Contemporary single chip microcomputer system is no longer only the bare metal environment in the development and use of a large number of dedicated embedded operating system is widely used in the full range of single chip microcomputer In PDAs and cell phones as the core processing of high end single chip or even a dedicated direct access to Windows and Linux operating systems More than a dedicated single chip processor suitable for embedded systems so it was up to the application In fact the number of single chip is the world s largest computer Modern human life used in almost every piece of electronic and mechanical products will have a single chip integration Phone telephone calculator home appliances electronic toys handheld computers and computer accessories such as a mouse in the Department are equipped with 1 2 single chip And personal computers also have a large number of single chip microcomputer in the workplace Vehicles equipped with more than 40 Department of the general single chip complex industrial control systems and even single chip may have hundreds of work at the same time SCM is not only far exceeds the number of PC and other integrated computing even more than the number of human beings Microcontrollers are used in a multitude of commercial applications such as modems motor control systems air conditioner control systems automotive engine and among others The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high speed event based applications However these critical application domains also require that these microcontrollers are highly reliable The high reliability and low market risks can be ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level Intel Plaform Engineering department developed an object oriented multi threaded test environment for the validation of its AT89C51 automotive microcontrollers The goals of this environment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers The environment was developed in conjunction with Microsoft Foundation Classes AT89C51 The 8 bit AT89C51 CHMOS microcontrollers are designed to handle high speed calculations and fast input output operations MCS 51 microcontrollers are typically used for high speed event control systems Commercial applications include modems motor control systems printers photocopiers air conditioner control systems disk drives and medical instruments The automotive industry use MCS 51 microcontrollers in engine control systems airbags suspension systems and antilock braking systems ABS The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on chip peripheral functions set such as automotive power train control vehicle dynamic suspension antilock braking and stability control applications Because of these critical applications the market requires a reliable cost effective controller with a low interrupt latency response ability to service the high number of time and event driven integrated peripherals needed in real time applications and a CPU with above average processing power in a single package The financial and legal risk of having devices that operate unpredictably is very high Once in the market particularly in mission critical applications such as an autopilot or anti lock braking system mistakes are financially prohibitive Redesign costs can run as high as a 500K much more if the fix means back annotating it across a product family that share the same core and or peripheral design flaw In addition field replacements of components is extremely expensive as the devices are typically sealed in modules with a total value several times that of the component To mitigate these problems it is essential that comprehensive testing of the controllers be carried out at both the component level and system level under worst case environmental and voltage conditions This complete and thorough validation necessitates not only a well defined process but also a proper environment and tools to facilitate and execute the mission successfully Intel Chandler Platform Engineering group provides post silicon system validation SV of various micro controllers and processors The system validation process can be broken into three major parts The type of the device and its application requirements determine which types of testing are performed on the device The AT89C51 provides the following standard features 4Kbytes of Flash 128 bytes of RAM 32 I O lines two 16 bittimer counters a five vector two level interrupt architecture a full duple ser ial port on chip oscillator and clock circuitry In addition the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes The Idle Mode stops the CPU while allowing the RAM timer counters serial port and interrupt sys tem to continue functioning The Power down Mode saves the RAM contents but freezes the oscil lator disabling all other chip functions until the next hardware reset Pin Configurations Block Diagram Pin Description VCC Supply voltage GND Ground Port 0 Port 0 is an 8 bit open drain bi directional I O port As an output port each pin can sink eight TTL inputs When 1s are written to port 0 pins the pins can be used as highimpedance inputs Port 0 may also be configured to be the multiplexed loworder address data bus during accesses to external program and data memory In this mode P0 has internal pullups Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification External pullups are required during program verification Port 1 Port 1 is an 8 bit bi directional I O port with internal pullups The Port 1 output buffers can sink so urce four TTL inputs When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs As inputs Port 1 pins that are externally being pulled low will source current IIL because of the internal pullups Port 1 also receives the low order address bytes during Flash programming and verification Port 2 Port 2 is an 8 bit bi directional I O port with internal pullups The Port 2 output buffers can sink source four TTL inputs When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs As inputs Port 2 pins that are externally being pulled low will source current IIL because of the internal pullups Port 2 emits the high order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current IIL because of the internal pullups Port 2 emits the high order address byte during fetches from external program memory and during accesses to external data memory that use 16 bit addresses MOVX DPTR In this application it uses strong internal pull ups when emitting 1s During accesses to external data memory that use 8 bit addresses MOVX RI Port 2 emits the contents of the P2 Special Function Register Port 2 also receives the high order address bits and some control signals durin Flash programming and verification Port 3 Port 3 is an 8 bit bi directional I O port with internal pullups The Port 3 output buffers can sink sou rce four TTL inputs When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs As inputs Port 3 pins that are externally being pulled low will source current IIL because of the pullups Port 3 also serves the functions of various special featuresof the AT89C51 as listed below Port PinAlternate Functions P3 0RXD serial input port P3 1TXD serial output port P3 2INT0 external interrupt 0 P3 3INT1 external interrupt 1 P3 4T0 timer 0 external input P3 5T1 timer 1 external input P3 6WR external data memory write strobe P3 7RD external data memory read strobe Port 3 also receives some control signals for Flash programming and verification RST Reset input A high on this pin for two machine cycles while the oscillator is running resets the device ALE PROG Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory This pin is also the program pulse input PROG during Flash programming In normal operation ALE is emitted at a constant rate of 1 6 the oscillator frequency and may be used for external timing or clocking purposes Note however that one ALE pulse is skipped duri ng each access to external DataMemory If desired ALE operation can be disabled by setting bit 0 of SFR location 8EH With the bit set ALE is active only during a MOVX or MOVC instruction Otherwise the pin is weakly pulled high Setting the ALE disable bit has no effect if the microcontroller is in external execution mode PSEN Program Store Enable is the read strobe to external program memory When the AT89C51 is executing code from external program memory PSEN is activated twice each machine cycle except that two PSEN activations are skipped during each access to external data memory EA VPP External Access Enable EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH Note however that if lock bit 1 is programmed EA will be internally latched on reset EA should be strapped to VCC for internal program executions This pin also receives the 12 volt programming enable voltage VPP during Flash programming for parts that require 12 volt VPP XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit XTAL2 Output from the inverting oscillator amplifier Oscillator Characteristics XTAL1 and XTAL2 are the input and output respectively of an inverting amplifier which can be configured for use as an on chip oscillator as shown in Figure 1 Either a quartz crystal or ceramic resonator may be used To drive the device from an external clock source XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2 There are no requirements on the duty cycle of the external clock signal since the input to the internal clocking circuitry is through a divide by two flip flop but minimum and maximum voltage high and low time specifications must be observed Idle Mode In idle mode the CPU puts itself to sleep while all the onchip peripherals remain active The mode is invoked by software The content of the on chip RAM and all the special functions registers remain