Emerson Liebert FPC Manuel d'utilisateur télécharger pdf (Page 8)

100

Modbus Communications

1.6 RTU Framing

The example below shows a typical query and response from a Liebert IntelliSlot 485 interface card.

The master device initiates a query asking Slave Device, with address 2, for holding registers

starting at holding register 40051 (offset 50) and including next 2 registers (3 total).

Table 4 Query sample

Slave

Address

Function

Code

Starting Register

Number of Registers

CRC16

Hi Byte

Lo Byte

Hi Byte

Lo Byte

Hi Byte

Lo Byte

Table 5 Response sample

Slave

Address

Function

Code

Count:

Bytes of

Data

CRC16

40051 Data

40052 Data

40053 Data

Hi Byte

Lo Byte

Slave Device, with address 2, responds to Function Code 3 with 6 bytes of hexadecimal data and

ends with CRC16 checksum.

40051 =

158(hex) =

344 (decimal)

40052 =

FA (hex) =

250 (decimal)

40053 =

54 (hex) =

84 (decimal)

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 99 100

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Emerson Liebert FPC Manuel d'utilisateur Page 8

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