Siemens SPC3 Specifications download pdf (Page 35)

Introduction To ProfiBus DP

___________________________________________________________________

_______________________________________________________________________________________

Acromag, Inc. Tel:248-624-1541 Fax:248-624-9234 Email:sales@acromag.com http://www.acromag.com

Unfreeze:

This control cancels the freeze command.

Clear_Data:

A class 1 master may use a global control telegram to inform

the slaves that it is switching from Operate Mode to Clear Mode. This

bit is set in Clear Mode (02 00H), and cleared in Operate Mode (00

00H). A slave will respond by either clearing its outputs, or it may

optionally assume a user-defined state with its master in Clear Mode.

Please refer to Failsafe Operation for more information on the use of

this bit.

DU Byte 2 (Group_Select or Group_Ident Number)

76543210

XXXXXXXX

Group_Select:

0-255, Number must match the Group_Ident number of

the parameterization data (multi-cast). If set to 0, all slaves are addressed

(broadcast).

Sync & Freeze are optional slave services and may not be supported by

some slaves. A master uses a Freeze telegram to make a slave or group of

slaves freeze their inputs in the current state. A Sync telegram causes the

output data currently available to be transferred to the outputs, to be frozen.

An Unsync & Unfreeze command will cancel this state. The Clear Data

service allows the outputs to be switched to a defined state if an error

occurs. The response parameter Status can be tested to indicate whether

transmission of the request frame was successful or not, with possible

values of: OK, DS, NO, and IV.

Use of Freeze

In closed-loop control systems and for the synchronization of drives,

etc., it is sometimes necessary to have a precise time image of the process

inputs of a group. Freeze is used to accomplish this as follows:

The master sends a Freeze command to the selected group

(A global

control telegram goes to the selected group at a precise time).

This causes

all addressed slaves to freeze their inputs. During the next Data Exchange

cycle, the slaves transfer the frozen inputs of the group to the master.

After the master receives this data, the master sends an Unfreeze

command to the group and the bus system returns to the normal data

exchange mode again, and all input changes are transferred during each

data cycle.

Use of Sync/Unsync

For the time-controlled operation of output devices which belong to a

group, sync and unsync are used as follows:

After the data is frozen with a Freeze command and has been

processed by the master, the master reacts by sending a sync command to

the slave group to obtain the outputs. During the next data cycle, the master

supplies the slave group with the data to be output, then concludes this cycle

with an unsync command in the following data exchange cycle. Unsync

causes the slaves to transfer their outputs at a precise time.

1 2 ... 30 31 32 33 34 35 36 37 38

Comments to this Manuals

No comments

Siemens SPC3 Specifications Page 35

Comments to this Manuals

Related products and manuals for Networking Siemens SPC3