Siemens SIMATIC TI500 Manual de usuario descargar pdf (Pagina 57)

Modbus Commands

C-8

TIWAY I Gateway User Manual

Modbus Function Descriptions (continued)

Code

02 allows the application to read a series of discrete inputs. The

command includes the start address and the number of points to be read.

Addressing is sequential up to the maximum memory size for a particular

PLC. The maximum number of inputs that can be addressed with one

command is 2000. If more are requested, the whole command will be

rejected with an Exception code 03.

Example:

I000000

Request: 07 02 000A 0005 XXXX

Checksum (XXXX)

Number of points (0005)

Start point (000A)

Function code (02)

Slave address (07)

Figur

e C-6

Read

Input Status Example — Request

This request is for the data from 5 discrete inputs (On/Off) starting at the

10th input.

[This command is equivalent to sending a TIW

Y I Primitive 20 request

using TT

-type 6 (Packed Discrete Inputs)].

I000000

Response: 07 02 01 1A XXXX

Checksum (XXXX)

Data (1A)

Number of bytes (01)

Function code (02)

Slave address (07)

Figur

e C-7

Read

Input Status Example — Response

Code 02 — Read

Input Status

1 2 ... 52 53 54 55 56 57 58 59 60 61 62 ... 93 94

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Siemens SIMATIC TI500 Manual de usuario Pagina 57