基于51單片機信號發生器的設計——外文翻譯(編輯修改稿)

　

【文章內容簡介】 respectively, of an inverting amplifier which can be configured for use as an onchip oscillator, as shown in Figure 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 are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a dividebytwo flipflop, but minimum and maximum voltage high and low time specifications must be observed. Figure 1. Oscillator Connections Configuration Figure2. External Clock Drive 4 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 onchip 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 hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. Onchip 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, 西安交通大學城市學院本科生 畢業設計（外文翻譯） the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory. 5 Powerdown Mode In the powerdown mode, the oscillator is stopped, and the instruction that invokes powerdown is the last instruction executed. The onchip RAM and Special Function Registers retain their values until the powerdown mode is terminated. The only exit from powerdown is a hardware reset. Reset redefines the SFRs but does not change the onchip 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. 6 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. 三、 Getting Started with 181。Vision2 The Keil Software 8051 development tools listed below are programs you use to pile your C code, assemble your assembly source files, link and locate object modules and libraries, create HEX files, and debug your target program. 181。Vision2 for Windows? is an Integrated Development Environment that bines project management, source code editing, and program debugging in one single, powerful environment. The C51 ANSI Optimizing C Cross Compiler creates relocatable object modules from your C source code. The SCM and 181。Vision2 The A51 Macro Assembler creates relocatable object modules from your 8051 assembly source code. The BL51 Linker/Locator bines relocatable object modules created by the C51 Compiler and the A51 Assembler into absolute object modules. The LIB51 Library Manager bines object modules into libraries that may be used by the linker. The OH51 ObjectHEX Converter creates Intel HEX files from absolute object modules. The RTX51 Realtime Operating System simplifies the design of plex, timecritical software projects. Software Development Cycle When you use the Keil Software tools, the project development cycle is roughly the same as it is for any other software development project. 1. Create a project, select the target chip from the device database, and configure the tool settings. 2. Create source files in C or assembly. 3. Build your application with the project manager. 4. Correct errors in source files. 5. Test the linked application. 181。Vision2 IDE The 181。Vision2 IDE bines project management, a richfeatured editor with interactive error correction, option setup, make facility, and online help. Use 181。Vision2 to create your source files and anize them into a project that defines your target application. 181。Vision2 automatically piles, assembles, and links your embedded application and provides a single focal point for your development efforts. LIB51 Library Manager The LIB51 library manager allows you to create object library from the object files created by the piler and assembler. Libraries are specially formatted, ordered program collections of object modules that may be used by the linker at a later time. When the linker processes a library, only those object modules in the library that are necessary to create the program are used. BL51 Linker/Locator The BL51 linker creates an absolute object module using the object modules extracted from libraries and those created by the piler and assembler. An absolute object file or module contains no relocatable code or data. All code and data reside at fixed memory locations. The absolute object file may be used: To program an EPROM or other memory devices, With the 181。Vision2 Debugger for simulation and target debugging, With an incircuit emulator for the program testing. 西安交通大學城市學院本科生 畢業設計（外文翻譯） 181。Vision2 Debugger The 181。Vision2 symbolic, sourcelevel debugger is ideally suited for fast, reliable program debugging. The debugger includes a highspeed simulator that let you simulate an entire 8051 system including onchip peripherals and external hardware. The attributes of the chip you use are automatically configured when you select the