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Chapter 2 Specification of Communication port for CPU module

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[Specifications of RS-422 and 485 of Serial communication]

Serial communication system of EHV-CPU is Half duplex. Half duplex is a communication system which can

transmit to only one direction of both directions communication. When the serial communication port for EHC=CPU

is used as a dedicated port, EHV-CPU repeats an operation of responding the request transmitted from the peripheral

device. Until the start of the receiving processing from the response end, the delay may occur. It is a communication

error because the receiving is not performed properly if the request is transmitted before the receiving is started.

For the safety communication, leave an interval of 2ms between the response end and the receiving processing start.

2ms or less

Peripheral device

EHV-CPU

Request

Response

Request

Cannot receive

Receiving

processing

Transmitting

processing

Receiving

processing

EHV-CPU inside

processing

Figure 2.37 Communication specifications of RS-422/485 of Serial communication

[Example]

In case of the serial communication to HMI (Human machine Interface) such as a touch panel and an indicator, set

the transmission wait on HMI when communication error occurs frequently in EHV-CPU.

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RTS WM300 Spezifikationen Seite 52