Saturday, July 9, 2011

The Child and Parent PLCs Generalized Data Transfer





The expansion link of I/O is basically a capability for contacting system wide I/O resources for a running logic program in a single PLC, the parent PLC. Though, since each child PLC on the connection has the ability to save its own user logic program and service its own communication and I/O ports, a convinced value of co-processing can happen in the a variety of CPUs on the connection.

Generalized data transfer is an instrument that permits the child and parent PLCs on the connection to distribute non- control data. It uses the cable links of the expansion link to transfer data to and from each other. The parent PLC can distribute generalized data with any and all child PLCs; a child PLC can distribute generalized data only with the parent PLC. The child and parent PLCs on an expansion network of I/O can bi-directionally pass a selectable number of non-control data words through the expansion network of I/O. Fixed I/O reference #5 on all Modicon Micro PLCs is kept for this transfer capability of generalized data. You can choose either the words of input/output to be kept in the User Data Memory of the child and parent PLCs by identifying one of the following reference types in the I/O maps of the child and parent PLC:
• MIC148, identifying one output word of 0x or 4x references and one input word of 1x or 3x references
• MIC149, identifying references two output words of 0x or 4x references and two input words of 1x or 3x
• MIC150, identifying four output words of 0x or 4x references and four input words of 1x or 3x references
• MIC151, identifying eight output words of 0x or 4x references and eight input words of 1x or 3x references

To set of connections a generalized data transfer between a child and parent PLC, you have to identify the same type of location in the I/O maps of the child PLC and of the parent PLC. When the panel of programming is linked to the parent PLC, identify the location type of generalized data transfer in the I/O map that explains the resources of fixed I/O of the child PLC, not in the I/O map that explains the resources of fixed I/O of the parent PLC.

In very small user logic test situations for example, using a contact to make a coil as a fast oscillator, in Child or Single mode process, the fast scan time may restrain proper operation of the internal output device circuit and the internal hardware output LED circuit.



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