Example of a simple ladder logic program
The Way of PLC memory Access to data
1. Bit, byte, Word and double word1-bit binary number (bit) value of 0 and 12 different, can be used to switch (or digital) of two different States, such as the contacts open and close coils powerup and powerdown. If the bit is 1, it means that the ladder diagram programming elements in coils "electricity", normally … Continue reading The Way of PLC memory Access to data
PLC Siemens series power requirements and calculations
S7-200 CPU module 5VDC 24VDC power supply:CPU when there are extension modules via the I/O bus to provide 5V power supply, 5V power consumption of all the extension modules and cannot exceed the power rating of the CPU to provide. If an external 5V power supply won't be enough. Each CPU has a 24VDC sensor … Continue reading PLC Siemens series power requirements and calculations
PLC Siemens series analog input (A1)
S7-200 analog values (such as temperature or voltage) into 1 Word (16-bit) number. Zone identifier (AI), the length of the data 
and the bytes of the start address to access these values. Because analog input for 1 Word, and an even number of bytes (for example, 0, 2, 4), must be even-numbered byte … Continue reading PLC Siemens series analog input (A1)
Siemens S200 PLC stores local variables (L)
Local variable storage variable storage is very similar, the main difference is that the local variable storage is partially valid, variable storage is global. Global refers to the same memory can be any program (such as the main program, interrupted procedures or subroutines) access, partially valid is stored and associated with specific programs. Local … Continue reading Siemens S200 PLC stores local variables (L)
Siemens PLC counter (c)
S7-200 CPU, counter to be accrued from the input port or the number of pulses sent by internal components. It has additional counters, counter and increase/decrease the counter 3 types. Due to the counter frequency scan cycle limitations, when you need to use high frequency to high frequency signal count counter (HSC).Counter has the following … Continue reading Siemens PLC counter (c)
Siemens PLC 200 special sign bits (SM)
Special flags to provide users with some special control function and system information, user's special requirements of operations also SM notification system. Special flag is divided into read-only and read-write in two parts. Read-only special flag, users can use their contacts, such as: SM0.0 RUN control, PLC in RUN State, SM0.0 is 1. SM0.1 initializes the pulse, … Continue reading Siemens PLC 200 special sign bits (SM)
Siemens PLC store (m)
In logical operations usually require some intermediate information element, they are not directly drive external load, intermediate staging effects, similar to a relay contact relay in the system. In the S7-200 series PLC, memory can be used as control relays to store the intermediate operational state and control information. General bits of the use.Store … Continue reading Siemens PLC store (m)
S7-200 PLC input relay
Enter a relay used to accept signals from external sensors or switches are special registers of the input image. It can only be driven by external signal driver. At the beginning of each scan cycle, CPU total physical input is sampled and sampled values written to the input register. Enter the relays generally used an … Continue reading S7-200 PLC input relay
S7-200 PLC Byte addressing, Addressing and Double word address
1) byte-addressed (8 bit) Byte addressable by the store identifier, identifier, a byte address combination of bytes. As VB100, its byte addressing mode as shown in the figure.Byte addressing format: [region ID] [-identifier].[-byte address] 2) addressing (16 bit) Addressed by the store identifier, identifier and byte the starting address combination. VW100, addressing mode as shown in the figure.Address … Continue reading S7-200 PLC Byte addressing, Addressing and Double word address
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