(2)Mechanical layout of the FX2N and expansion I/O modules (including cabinets and other equipment
(3)Electrical drawings for each FX2N and expansion I/O module (including the device model numbers, communications addresses, and I/O addresses)
Create a List of Symbolic Names (optional)
If you choose to use symbolic names for addressing, create a list of symbolic names for the absolute addresses. Include not only the physical I/O signals, but also the other elements to beused in your program.
Basic Elements of a Program.
A program block is composed of executable code and comments. The executable code consists of a main program and any subroutines or interrupts routines. The code is compiled and downloaded to the FX2N; the program comments are not. You can use the organizational elements (main program, subroutines, and interrupt routines) to structure your control program.
 Main Program
The main body of the program contains the instructions that control your application. The FX2N executes these instructions sequentially, once per scan cycle.
Subroutines.
These optional elements of your program are executed only when called: by the main program, by an interrupt routine, or by another subroutine. Subroutines are useful in cases where you want to execute a function repeatedly. Rather than rewriting the logic for each place in the main program where you want the function to occur, you can write the logic once in a subroutine and call the subroutine as many times as needed during the main program. Subroutines provide several benefits:
(1)Using subroutines reduces the overall size of your program.
(2)Using subroutines decreases your scan time because you have moved the code out of the main program. The FX2N evaluates the code in the main program every scan cycle, whether the code is executed or not, but the FX2N evaluates the code in the subroutine only when you call the subroutine, and does not evaluate the code during the scans in which the subroutine is not called.
(3)Using subroutines creates code that is portable. You can isolate the code for a function in a subroutine, and then copy that subroutine into other programs with little or no rework.
Interrupt Routines
These optional elements of your program react to specific interrupt events. You design an interrupt routine to handle a pre-defined interrupt event. Whenever the specified event occurs, the FX2N executes the interrupt routine. The interrupt routines are not called by your main program. You associate an interrupt routine with an interrupt event, and the FX2N executes the instructions in the interrupt routine only on each occurrence of the interrupt event.
Installing the PLC
The FX2N equipment is designed to be easy to install. You can use the mounting holes to attach the modules to a panel, or you can use the built-in clips to mount the modules onto a standard (DIN) rail. The small size of the FX2N allows you to make efficient use of space.
Guidelines for Installing FX2N Devices
You can install an FX2N either on a panel or on a standard rail, and you can orient the FX2N either horizontally or vertically.
Separate the FX2N Devices from Heat, High Voltage, and Electrical Noise
As a general rule for laying out the devices of your system, always separate the devices that generate high voltage and high electrical noise from the low-voltage, logic-type devices such as the FX2N.
When configuring the layout of the FX2N inside your panel, consider the heat-generating devices and locate the electronic-type devices in the cooler areas of your cabinet. Operating any electronic device in a high-temperature environment will reduce the time to failure.
Consider also the routing of the wiring for the devices in the panel. Avoid placing low voltage signal wires and communications cables in the same tray with AC power wiring and high-energy, rapidly-switched DC wiring.
Provide Adequate Clearance for Cooling and Wiring FX2N devices are designed for natural convection cooling. For proper cooling, you must provide a clearance of at least 25 mm above and below the devices. Also, allow at least 75 mm of depth. PLC可编程控制器英文参考文献和中文翻译(4):http://www.751com.cn/fanyi/lunwen_3792.html