Rockwell-automation 900 Temperature Controller Communications Function Uživatelský manuál stáhnout pdf (Strana 63)

Publication 900-UM004D-EN-E - July 2010

Modbus Communications Procedure 4-5

No Response

In the following cases, the received command will not be processed and a

response will not be returned.

Consequently, a timeout error will occur at the host device.

· The slave address in the received command does not match the

communications unit number.

· A parity error, framing error, or overrun error occurred due to a

problem such as a transfer error.

· A CRC-16 code error occurred in the received command frame.

· There was a time interval of more than 3.5 character times between data

packets that make up the command frame.

Furthermore, the specified function’s processing will be performed but no

response will be returned for broadcast functions (slave address = H’00).

Function List

The following table lists the function codes.

Table 4.4 Function Code List

Function Code Name Process

03 (H’03) Read variable

(multiple)

This function reads from variable areas.

It is possible to read two or more consecutive

variables.

16 (H’10) Write variable

(multiple)

This function writes to variable areas.

It is possible to write two or more consecutive

variables.

It is also possible to broadcast this function

(broadcast transmission).

06 (H’06) Write variable

(single/operation

command)

This function writes to the variable area and writes

operation commands.

It is also possible to write to a single parameter by

specifying the address in 2-byte mode. (This is not

supported in 4-byte mode.)

It is also possible to broadcast this function

(broadcast transmission.)

8 (H’008) Echoback Test This function performs an echoback test.

1 2 ... 58 59 60 61 62 63 64 65 66 67 68 ... 102 103

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Rockwell-automation 900 Temperature Controller Communications Function Uživatelský manuál Strana 63