Siemens SIMATIC TI505 Manual de usuario descargar pdf (Pagina 39)

Modbus Commands

2-8

SIMATIC TI505/TI500 MODNIM User Manual

2.4 Modbus Function Descriptions

the descriptions that follow

, each function starts on a separate page and

includes the TIW

Y primitive sent to the secondary in square brackets. For

each function, an example of request and response is given.

NOTE: As Mode-specific data is not given, each of these examples omits the

header ( : ) and tail (CR/LF) of ASCII mode.

Code 01 enables the user to read the On/Off values of logic coils. The data

passed with this command is the start address and the number of coils to be

read. Addressing is sequential up to the maximum memory size for a

particular PLC. The maximum number of coils that can be addressed with

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

rejected with an Exception code 03.

SIMATIC

TI PLCs number memory locations starting at address 1.

Modbus PLCs number areas of memory starting from address 0.

Failure to alter host computer application programs may result in

the wrong bits being read.

Example:

Request: 07 01 000A 0005 XXXX

Checksum (XXXX)

Number of points (0005)

Start point (000A)

Function code (01)

Slave address (07)

Figure 2-4 Read

Coil Status Example — Request

This request is asking the MODNIM to return the data from 5 coils (On/Off)

starting at the 10th coil.

[This is equivalent to sending a TIW

Y Primitive 20 request using TT

-type 7

(Packed Discrete Outputs or Ys) or TT

-type 8 (Packed Cs), depending on the

position of Switch 10 of the network dipswitch bank in the MODNIM.]

Introduction

Code 01 — Read

Coil Status

CAUTION

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 90 91

Sin comentarios

Siemens SIMATIC TI505 Manual de usuario Pagina 39