Programmable logic controller with building blocks

Abstract

The present invention provides a block type PLC which adopts a communication mode that is affected less by the in-bit staggering, crosstalk, earth wire bouncing and the like and will not reduces the transmitting performance even the number of the connecting module is increased. The switch module which is not installed with a CPU system, the CPU module and a plurality of equipment modules are connected integratedly through a specified module connecting mechanism for realizing the block structure. A star-shaped serial communication network which takes the switch module that is not installed with a CPU system as a central node and takes the CPU module and each equipment module of the plurality of equipment modules as perimeter node is constructed.

Description

technical field [0001] The present invention relates to a building block type programmable controller (hereinafter referred to as PLC), which prepares a CPU module (also referred to as a unit) with equipment modules having various functions (for example, IO modules, analog 10 modules, processing (process) IO modules, motion control modules, processing CPU modules, various communication modules supporting communication protocols, etc.), by appropriately selecting these equipment modules and integrally connecting them with a prescribed inter-module connection mechanism, thereby It can flexibly respond to a wide range of control specifications on the user side. Background technique [0002] Conventionally, a block type PLC is known in which equipment modules having various functions are prepared for the CPU module, and these equipment modules are appropriately selected and integrally connected by a predetermined inter-module connection mechanism, thereby enabling flexible handl...

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Problems solved by technology

[0021] However, when communicating between modules using the parallel bus method shown in Fig. 10, due to the influence of bit interleaving, crosstalk, ground bounce, etc., the increase in communication speed reaches its limit.

In addition, even when inter-module communication is performed by the serial bus method shown in Fig. 11, there is a limit to speeding up due to signal degradation and ground bouncing in the 1-to-N connection

Furthermore, when inter-module communication is performed by the storage relay method via the adjacent inter-module connection lines (SCL1, SCL2), there is a problem that communication with all modules cannot be performed due to a failure of a module in the middle.

In addition, the following problems have been pointed out: when using these buses or connecting lines between adjacent modules, due to constraints from the original structure of the bus system in which data from a plurality of modules flows into a common communication line, as As the number of connected modules increases, the transmission performance decreases significantly

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