【正文】 e, your program is executed。 in STOP mode, your program is not executed.Reading the InputsDigital inputs: Each scan cycle begins by reading the current value of the digital inputs and then writing these values to the processimage input register. Analog inputs: The S7200 does not update analog inputs from expansion modules as part of the normal scan cycle unless filtering of analog inputs is enabled. An analog filter is provided to allow you to have a more stable signal. You can enable the analog filter for each analog input point. When analog input filtering is enabled for an analog input, the S7200 updates that analog input once per scan cycle, performs the filtering function, and stores the filtered value internally. The filtered value is then supplied each time your program accesses the analog input. When analog filtering is not enabled, the S7200 reads the value of the analog input from expansion modules each time your program accesses the analog input. Analog inputs AIW0 and AIW2 included on the CPU 224XP are updated every scan with the most recent result from the analogtodigital converter. This converter is an averaging type (sigmadelta) and those values will usually not need software filtering.Executing the ProgramDuring the execution phase of the scan cycle, the S7200 executes your program, starting with first instruction and proceeding to the end instruction. The immediate I/O instructions give you immediate access to inputs and outputs during the execution of either the program or an interrupt routine. If you use interrupts in your program, the interrupt routines that are associated with the interrupt events are stored as part of the program. The interrupt routines are not executed as part of the normal scan cycle, but are executed when the interrupt event occurs (which could be at any point in the scan cycle).Processing Any Communications RequestsDuring the messageprocessing phase of the scan cycle, the S7200 processes any messages that were received from the munications port or intelligent I/O modules. Executing the CPU Selftest Diagnostics During this phase of the scan cycle, the S7200 checks for proper operation of the CPU and for the status of any expansion modules.Writing to the Digital OutputsAt the end of every scan cycle, the S7200 writes the values stored in the processimage output register to the digital outputs. (Analog outputs are updated immediately, independently from the scan cycle.)Accessing the Data of the S7200The S7200 stores information in different memory locations that have unique addresses. You can explicitly identify the memory address that you want to access. This allows your program to have direct access to the information. Table 1 shows the range of integer values that can be represented by the different sizes of data.To access a bit in a memory area, you specify the address, which includes the memory area identifier, the byte address, and the bit number. Figure 3 shows an example of accessing a bit (which is also called “byte. bit” addressing). In this example, the memory area and byte address(I = input, and 3 = byte 3) are followed by a period (“.”) to separate the bit address (bit 4).You can access data in most memory areas (V, I, Q, M, S, L, and SM) as bytes, words, or double words by using the Byteaddress format. To access a byte, word, or double wordTable 1 Decimal and Hexadecimal Ranges for the Different Sizes of DataRepresentationByte (B)Word (W)Double Word (D)UnsignedInteger0to2550toFF0 to 65,5350 to FFFF0to4,294,967,290toFFFF FFFFSigned Integer128to+127 80 to 7F32,768to+32,7678000 to 7FFF2,147,483,648 to+2,147,483,64780000000to7FFFFFFFRealIEEE 32bitFloating PointNot applicableNot applicable+—38to++38 (positive)++38 (negative)in the memory, you must specify the address in a way similar to spec ifying the address for a bit. This includes an area identifier, data size designation, and the starting byte address of the byte, word, or doubleword value.Accessing Data in the Memory Areas216。 ProcessImage Input Register: IThe S7200 samples the physical input points at the beginning of each scan cycle and writes these values to the processimage input register. You can access the processimage input register in bits, bytes, words, or double words:Bit: I[byte address].[bit address] Byte, Word, or Double Word: I[size][starting byte address] IB4216。 ProcessImage Output Register: QAt the end of the scan cycle, the S7200 copies the values stored in the processimage output register to the physical output points. You can access the processimage output register in bits, bytes, words, or double words:Bit: Q[byte address].[bit address] Byte, Word, or Double Word: Q[size][starting byte address] QB5216。 Variable Memory Area: VYou can use V memory to store intermediate results of operations being performed by the control logic in your program. You can also use V memory to store other data pertaining to your process or task. You can access the V memory area in bits, bytes, words, or double words: Bit: V[byte address].[bit address] Byte, Word, or Double Word: V[size][starting byte address] VW100216。 Bit Memory Area: MYou can use the bit memory area (M memory) as control relays to store the intermediate status of an operation or other control information. You can access the bit memory area in bits, bytes, words, or double words:Bit: M[byte address].[bit address] Byte, Word, or Double Word: M[size][starting byte address] MD20216。 Timer Memory Area: TThe S7200 provides timers that count increments of time in resolutions (timebase increments) of 1ms, 10 ms, or 100ms. Two variables are associated with a timer:u Current value: this 16bit signed integer stores the amount of time counted by the timer.u Timer bit: this bit is set or cleared as a re