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1、 2007 级毕业（设计）论文 信息工程学院 系（院） 电子信息工程 专业 中英文献翻译 题 目 基于超声波检测的倒车雷达设计（硬件设计） 学 生 姓 名 班 级 2007电子信息工程 学 号 指 导 教 师 日 期 2011 年 03 月 21 日 教 务 处 订 制AT89C2051 Microcontroller Instructions1.1 Features Compatible with MCS-51 Products 2 Kbytes of Reprogrammable Flash MemoryEndurance: 1,000 Write/Erase Cycles 2.7 V t
2、o 6 V Operating Range Fully Static Operation: 0 Hz to 24 MHz Two-Level Program Memory Lock 128 x 8-Bit Internal RAM 15 Programmable I/O Lines Two 16-Bit Timer/Counters Six Interrupt Sources Programmable Serial UART Channel Direct LED Drive Outputs On-Chip Analog Comparator Low Power Idle and Power D
3、own Modes1.2 DescriptionThe AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2 Kbytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard
4、 MCS-51 instruction set and pinout. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.The AT89C2051 provides the following standard fea
5、tures: 2 Kbytes of Flash, 128 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In addition, the AT89C2051 is designed with static logic for operatio
6、n 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 ch
7、ip functions until the next hardware reset.1.3 Pin Configuration 1.4 Pin DescriptionVCC Supply voltage.GND Ground.Port 1Port 1 is an 8-bit bidirectional I/O port. Port pins P1.2 to P1.7 provide internal pullups. P1.0 and P1.1 require external pullups. P1.0 and P1.1 also serve as the positive input (
8、AIN0) and the negative input (AIN1), respectively, of the on-chip precision analog comparator. The Port 1 output buffers can sink 20 mA and can drive LED displays directly. When 1s are written to Port 1 pins, they can be used as inputs. When pins P1.2 to P1.7 are used as inputs and are externally pu
9、lled low, they will source current (IIL) because of the internal pullups.Port 1 also receives code data during Flash programming and program verification.Port 3Port 3 pins P3.0 to P3.5, P3.7 are seven bidirectional I/O pins with internal pullups. P3.6 is hard-wired as an input to the output of the o
10、n-chip comparator and is not accessible as a general purpose I/O pin. The Port 3 output buffers can sink 20 mA. 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 (
11、IIL) because of the pullups. Port Pin Alternate FunctionsP3.0RXD (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)Port 3 also serves the functions of various special features of
12、the AT89C2051 as listed below:1.5 Oscillator CharacteristicsXTAL1 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
13、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 divideby-two flip-flop, but minimum and maximum voltag
14、e high and low time specifications must be observed.1.6 Special Function RegistersA map of the on-chip memory area called the Special Function Register (SFR) space is shown in the table below. Note that not all of the addresses are occupied, and unoccupied addresses may not be implemented on the chi
15、p. Read accesses. to these addresses will in general return random data, and write accesses will have an indeterminate effect.User software should not write 1s to these unlisted locations, since they may be used in future products to invoke new fea tures. In that case, the reset or inactive values o
16、f the new bits will always be 0.1.7 Restrictions on Certain InstructionsThe AT89C2051 and is an economical and cost-effective member of Atmels growing family of microcontrollers. It contains 2 Kbytes of flash program memory. It is fully compatible with the MCS-51 architecture, and can be programmed
17、using the MCS-51 instruction set. However, there are a few considerations one must keep in mind when utilizing certain instructions to program this device.All the instructions related to jumping or branching should be restricted such that the destination address falls within the physical program mem
18、ory space of the device, which is 2K for the AT89C2051. This should be the responsibility of the software programmer. For example, LJMP 7E0H would be a valid instruction for the AT89C2051 (with 2K of memory), whereas LJMP 900H would not.1. Branching instructions:LCALL, LJMP, ACALL, AJMP, SJMP, JMP A
19、+DPTRThese unconditional branching instructions will execute correctly as long as the programmer keeps in mind that the destination branching address must fall within the physical boundaries of the program memory size (locations 00H to 7FFH for the 89C2051). Violating the physical space limits may c
20、ause unknown program behavior.CJNE ., DJNZ ., JB, JNB, JC, JNC, JBC, JZ, JNZ With these conditional branching instructions the same rule above applies. Again, violating the memory boundaries may cause erratic execution.For applications involving interrupts the normal interrupt service routine addres
21、s locations of the 80C51 family architecture have been preserved.2. MOVX-related instructions, Data Memory:The AT89C2051 contains 128 bytes of internal data memory. Thus, in the AT89C2051 the stack depth is limited to 128 bytes, the amount of available RAM. External DATA memory access is not support
22、ed in this device, nor is external PROGRAM memory execution. Therefore, no MOVX . instructions should be included in the program.A typical 80C51 assembler will still assemble instructions, even if they are written in violation of the restrictions mentioned above. It is the responsibility of the cont
23、roller user to know the physical features and limitations of the device being used and adjust the instructions used correspondingly.1.8 Program Memory Lock BitsOn the chip are two lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the ta
24、ble below:Lock Bit Protection Modes(1) Program Lock BitsLB1LB2Protection Type1UUNo program lock features.2PUFurther programming of theFlash is disabled.3PPSame as mode 2, also verifyis disabled.Note: 1. The Lock Bits can only be erased with the Chip Erase operation1.9 Idle ModeIn idle mode, the CPU
25、puts itself to sleep while all the on-chip peripherals remain active. The mode is invoked by software. The content of the on-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.P1.0 and P1
26、.1 should be set to 0 if no external pullups are used, or set to 1 if external pullups are used.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 tak
27、es 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 wri
28、tes to a port pin or to external memory.1.10 Power Down ModeIn 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
29、only exit from power down is a hardware reset. Reset redefines the SFRs 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.P1.0 and P1.1 shoul
30、d be set to 0 if no external pullups are used, or set to 1 if external pullups are used.1.11 Programming The FlashThe AT89C2051 is shipped with the 2 Kbytes of on-chip PEROM code memory array in the erased state (i.e., contents = FFH) and ready to be programmed. The code memory array is programmed o
31、ne byte at a time. Once the array is programmed, to re-program any non-blank byte, the entire memory array needs to be erased electrically.Internal Address Counter: The AT89C2051 contains an internal PEROM address counter which is always reset to 000H on the rising edge of RST and is advanced by app
32、lying a positive going pulse to pin XTAL1.Programming Algorithm: To program the AT89C2051, the following sequence is recommended.1. Power-up sequence:Apply power between VCC and GND pins Set RST and XTAL1 to GNDWith all other pins floating, wait for greater than 10 milliseconds2. Set pin RST to H Se
33、t pin P3.2 to H3. Apply the appropriate combination of H or L logic levels to pins P3.3, P3.4, P3.5, P3.7 to select one of the programming operations shown in the PEROM Programming Modes table.To Program and Verify the Array:4. Apply data for Code byte at location 000H to P1.0 to P1.7. 5. Raise RST
34、to 12V to enable programming.6. Pulse P3.2 once to program a byte in the PEROM array or the lock bits. The byte-write cycle is self-timed and typically takes 1.2 ms.7. To verify the programmed data, lower RST from 12V to logic H level and set pins P3.3 to P3.7 to the appropiate levels. Output data c
35、an be read at the port P1 pins.8. To program a byte at the next address location, pulse XTAL1 pin once to advance the internal address counter. Apply new data to the port P1 pins.9. Repeat steps 5 through 8, changing data and advancing the address counter for the entire 2 Kbytes array or until the e
36、nd of the object file is reached.10. Power-off sequence: set XTAL1 to L set RST to LFloat all other I/O pins Turn Vcc power offData Polling: The AT89C2051 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 c
37、omplement of the written data on P1.7. Once the write cycle has been completed, true data is valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy: The Progress of byte programming can also be monitored by the RDY/BSY ou
38、tput signal. Pin P3.1 is pulled low after P3.2 goes High during programming to indicate BUSY. P3.1 is pulled High again when programming is done to indicate READY.Program Verify: If lock bits LB1 and LB2 have not been programmed code data can be read back via the data lines for verification:1. Reset
39、 the internal address counter to 000H by bringing RST from L to H.2. Apply the appropriate control signals for Read Code data and read the output data at the port P1 pins.3. Pulse pin XTAL1 once to advance the internal address counter.4. Read the next code data byte at the port P1 pins. 5. Repeat st
40、eps 3 and 4 until the entire array is read.The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.Chip Erase: The entire PEROM array (2 Kbytes) and the two Lock Bits are erased electrically by using the proper combination of
41、control signals and by holding P3.2 low for 10 ms. The code array is written with all 1s in the Chip Erase operation and must be executed before any non-blank memory byte can be re-programmed.Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of
42、locations 000H, 001H, and 002H, except that P3.5 and P3.7 must be pulled to a logic low. The values returned are as follows.(000H) = 1EH indicates manufactured by Atmel (001H) = 21H indicates 89C2051Programming InterfaceEvery code byte in the Flash array can be written and the entire array can be er
43、ased by using the appropriate combination of control signals. The write operation cycle is self-timed and once initiated, will automatically time itself to completion.All major programming vendors offer worldwide support for the Atmel microcontroller series. Please contact your local programming ven
44、dor for the appropriate software revision.Ultrasonic ranging system designPublication title: Sensor Review. Bradford: 1993. Vol. ABSTRACT：Ultrasonic ranging technology has wide using worth in many fields，such as the industrial locale，vehicle navigation and sonar engineeringNow it has been used in le
45、vel measurement，self-guided autonomous vehicles, fieldwork robots automotive navigation，air and underwater target detection，identification，location and so onSo there is an important practicing meaning to learn the ranging theory and ways deeply. To improve the precision of the ultrasonic ranging sys
46、tem in hand，satisfy the request of the engineering personnel for the ranging precision，the bound and the usage，a portable ultrasonic ranging system based on the single chip processor was developedKeywords：Ultrasound r，Ranging System，Single Chip Processor1.IntroductiveWith the development of science
47、and technology, the improvement of peoples standard of living, speeding up the development and construction of the city. urban drainage system have greatly developed their situation is constantly improving. However, due to historical reasons many unpredictable factors in the synthesis of her time, the city drainage system. In particular drainage system often lags behind urban construction. Therefore, there are often good building excavation has been building facilities to upgrade the drainage system phenomenon. It brought to
