AT89C51的介绍外文翻译.doc

外文资料原文
Introduction of AT89C51
Description:
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the ATMEL Co.’s AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.
Features:
·Compatible with instruction set of MCS-51 products
·4K bytes of in-system reprogrammable Flash memory
·Endurance: 1000 write/erase cycles
·Data retention time: 10 years
·Fully static operation: 0 Hz to 24 MHz
·Three-level program memory lock
·128×8-bit internal RAM
·32 programmable I/O lines
·Two 16-bit Timer/Counters
·Six interrupt source
·Programmable serial channel
·Low-power idle and Power-down modes
·On-chip oscillator and clock circuitry
·Full-duplex UART serial port interrupt line
·Dual Data Pointer Register
Function Characteristic Description:
The AT89C51 provides the following standard features: 4K bytes of Flash memory, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial 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 system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.
The 8051 microcontroller is an industry standard architecture that has broad acceptance, wide-ranging applications and development tools available. There are numerous commercial vendors that supply this controller or have it integrated into some type of system-on-a-chip structure. Both MRC and IAμE chose this device to demonstrate two distinctly different technologies for hardening. The MRC example of this is to use temporal latches that require specific timing to ensure that single event effects are minimized. The IAμE technology uses ultra low power, and layout and architecture HBD design rules to achieve their results. These are fundamentally different than the approach by Aeroflex-United Technologies Microelectronics Center (UTMC), the commercial vendor of a radiation– hardened 8051, that built their 8051 microcontroller using radiation hardened processes. This broad range of technology within one device structure makes the 8051an ideal vehicle for performing this technology evaluation
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 high impedance inputs.
Port 0 may also be configured to be the multiplexed low order address/bus during accesses to external program and data memory. In this mode P0 has internal pull ups.
Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull ups are required during program verification.
·Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull ups 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 pull ups.
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 pull ups. 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 pull ups 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 pull ups.
Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory which uses 16-bit addresses (MOVX @ DPTR). In this application, it uses strong internal pull ups when emitting 1s. During accesses to external data memory which uses 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 during 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/source four TTL inputs. When the P3 I write "1" after, they are internal pull-up is high, and used as input. As input, due to the external pull-down for the low, P3 port output current (ILL) This is due to pull-up's sake.
Port 3 also serves the functions of various special features of the AT89C51 as listed below:

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/: 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 () 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 during each access to external Data Memory.
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.
·：Program Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, is activated twice each machine cycle, except that two 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. When / EA to maintain low, then during this period the external program memory (0000H-FFFFH), regardless of whether an internal program memory.
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.
·Ready/: The progress of byte programming can also be monitored by the RDY/output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.
Oscillator Characteristics：
XTAL1 and XTAL2 respectively, reverse amplifier input and output. The reverse amplifier can be configured as on-chip oscillator. Shi Jing oscillation ceramic oscillation can be used. If using an external clock source drive the device, XTAL2 should not take. More than input to the internal clock signal through a two-way flip-flop, so the external clock signal pulse width without any request, but must ensure that the high-low pulse width requirements.
Clock Oscillator：
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator. 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.
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 trigger, 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 on-chip peripherals remain active. The mode is invoked by software. The content of the chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset.
It should be noted that when idle is terminated by a hardware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.
Power-down Mode:
In the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and special function registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the special function registers but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.
Program Memory Lock Bits:
On the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below.

When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.
Programming the Flash:
The AT89C51 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low-voltage programming mode provides a convenient way to program the AT89C51 inside the user’s system, while the high-voltage programming mode is compatible with conventional third party Flash or EPROM programmers.The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled.
The AT89C51 code memory array is programmed byte-by-byte in either programming mode. To program any nonblank byte in the on-chip Flash memory, the entire memory must be erased using the chip erase mode.
Programming Algorithm:
Before programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table .To program the AT89C51, take the following steps:
1. Input the desired memory location on the address lines.
2. Input the appropriate data byte on the data lines.
3. Activate the correct combination of control signals.
4. Raise EA/VPP to 12V for the high-voltage programming mode.
5. Pulse ALE/once to program a byte in the Flash array or the lock bits.
The byte-write cycle is self-timed and typically takes no more than 1.5ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached.
Data Polling:
The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data valid on all outputs, and the next cycle may begin. Data polling may begin any time after a write cycle has been initiated.
Program Verify:
If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.
Chip Erase:
The whole array and three lock-bit PEROM electrical erase control signals through the right combination and maintain ALE pin is low 10ms to complete. Cleaning operation in the chip, code arrays were all written "1" and in any non-empty memory byte has been programmed to repeat the past, the operation must be executed. In addition, AT89C51 with steady-state logic, and can be in the low to zero frequency under the conditions of static logic, and supports two software selectable power-down mode. In idle mode, CPU stop working. But the RAM, timers, counters, serial port and interrupt system are still working. In the power-down mode, to save the contents of RAM and a freeze oscillator, to prohibit the use of other chip functions until the next until a hardware reset.
Reading the Signature Bytes:
The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as follows:
(030H) = 1EH indicates manufactured by ATMEL
(031H) = 51H indicates AT89C51 single-chip
(032H) = FFH indicates 12V programming
(032H) = 05H indicates 5V programming
Programming Interface:
Every code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is self timed and once initiated, will automatically time itself to completion.
Watchdog (WDT) circuit:
Watchdog (WDT) reset circuit is to achieve the main functionality. When the MCU is running an infinite loop occurs when the watchdog (WDT) can play a protection circuit to achieve reduction effect.

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外文资料译文：
AT89C51的介绍
描述：
AT89C51是一个低电压，高性能CMOS8位单片机带有4K字节的可反复擦写的程序存储器（PENROM）。和128字节的存取数据存储器（RAM），这种器件采用ATMEL公司的高密度、不容易丢失存储技术生产，并且能够与MCS-51系列的单片机兼容。片内含有8位中央处理器和闪烁存储单元，功能强大AT89C51单片机可为您提供许多高性价比的应用场合，可灵活应用于各种控制领域。
主要性能参数：
·与MCS-51产品指令系统完全兼容
·4K字节可重擦写Flash闪速存储器
·1000次擦写周期
·数据保留时间：10年
·全静态操作：0Hz—24MHz
·三级加密程序存储器
·128×8字节内部RAM
·32个可编程I/O口线
·2个16位定时/计数器
·6个中断源
·可编程串行UART通道
·低功耗空闲和掉电模式
·片内振荡器和时钟电路
·全双工UART串行中断口线
·双数据寄存器指针
功能特性概述：
AT89C51提供以下标准功能：4K字节Flash闪速存储器，128字节内部RAM，32个I/O口线，两