Siemens SIMATIC TI500 Manual de usuario descargar pdf (Pagina 52)

Modbus Commands

C-3

TIWAY I Gateway User Manual

The

start and finish of a message is determined by timing in RTU mode.

Any time longer than 3.5 character lengths marks the end of a

transmission. The next character after that would then mark the start of

the next message. This time period is dependent on the baud rate. T

able C-2

shows the effect of baud rate on the time period (assuming 2 stop bits).

able C-2

TU T

iming

Baud Rate Time (ms)

19200

9600

7200

4800

3600

2400

1800

1200

600

300

200

150

110

2.2

4.4

5.9

8.8

11.7

17.5

23.4

35.0

70.0

140.0

210.0

280.0

383.0

The

Address field identifies the node to which this message is being sent

and is a number in the range of 1 to 247. Each node on any one network

must have a unique address. Only those nodes addressed will respond

unless the broadcast address 0 is used. In that case, each slave will read

and act on the message but not respond.

The Function field is an 8-bit code that determines the action that a slave

takes when receiving the message. These function codes are summarized in

able C-1 and described in more detail with examples in section C.2.

The Data field contains the information needed by the specified node to

perform the required operation, or the information returned by the node to

the host computer

The checksum needs 16 bits and uses the Cyclic Redundancy Checksum

(CRC) method. The calculation of this checksum is described in the

Modbus

Protocol Reference Manual

Message

Delineation

The Addr

ess Field

The Function Field

The Data Field

Checksum

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 93 94

Comentarios a estos manuales

Sin comentarios

Siemens SIMATIC TI500 Manual de usuario Pagina 52

Comentarios a estos manuales

Relacionado con productos y manuales para Gateways / Controladores Siemens SIMATIC TI500