FOXBORO I/A Series P0971WV Dual Node Bus Module

Description

When the PLC is running, it completes control tasks by executing user programs that reflect control requirements, requiring the execution of numerous operations. However, the CPU cannot perform multiple operations simultaneously. It can only execute one operation at a time in a time-sharing (serial work) manner, one at a time, in sequence. Due to the fast processing speed of the CPU, from a macro perspective, the results that appear outside of the PLC seem to be completed simultaneously (in parallel). This serial working process is called the scanning working mode of PLC.

When using scanning mode to execute user programs, scanning starts from the first program and, without interruption or jump control, executes user programs one by one in the order of program storage until the program ends. Then scan and execute from scratch, repeating the process over and over again.

The scanning working mode of PLC is significantly different from the working principle of electrical control. The electrical control device adopts a hard logic parallel working mode. If the coil of a relay is powered on or off, all normally open and normally closed contacts of the relay will immediately act simultaneously regardless of which position they are in the control circuit; The PLC adopts a scanning working mode (serial working mode). If the coil of a soft relay is connected or disconnected, all its contacts will not immediately act and must wait until the scanning reaches that point before it can act. However, due to the fast scanning speed of PLC, there is usually no difference in the I/O processing results between PLC and electrical control devices.

5X00529G02
5X00497G01
5X00481G04
5X00481G01
5X00357G04
5X00321G01
5X00301G01/5X00327G01
5X00301G01
5X00300G01/5X00321G01
5X00300G01
5X00241G01
5X00226G03
5X00226G01
5X00225G01
5X00167G01
5X00119G01/5X00121G01
5X00119G01
5X00070G04/1C31116G04
5X00070G01
5X00059G01
5X00058G01