Toho-electronics TTM000 Manual do Utilizador descarregar pdf (Página 20)

6. MODBUS communications control

6.1 Communications procedure

This product returns a "response message" in response to a "request message" from a high-level

computer. It therefore does not initiate a transmission.

6.2 Message types

Messages are roughly divided into the following types:

Read request message

Write request message

Store request message

Request message (transmitted

from a high-level computer)

Response message (transmitted

from this product)

Receipt acknowledgement and data

response

Write complete response

Reception error and error description

response

Store complete response

: Response when a normal "request message" is received

: When a received "request message" contains an error

In RTU codes, the data is binary.

In ASCII codes, all codes are expressed in ASCII codes.

In assembling a program for a high-level computer, see "9. Table of identifiers (codes)" and "10.

Table of ASCII codes" at the end of the book.

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