Спецификация протокола Profibus

Page 701

PROFIBUS-Specification-Normative-Parts-8:1997

Before commissioning a DP-system, all stations shall have been assigned an

unique address. In the case of DP-Slaves, this address can be set up via bus

(see section "Change Station Address of a DP-Slave").

All DP-Slaves that have not yet been assigned an individual address, start with

default address 126. Only one device with this address is allowed on the network

at a certain time. It is not allowed to set a DP-Master address to the default

address. A DP-Master (class 2) can access a Slave via that address and can

assign a specific address to that device.

For security reasons, the DP-Master (class 1) shall not exchange I/O-data with a

DP-Slave whose address is 126.

To exchange I/O data a DP-Master (class 1) shall have a valid master parameter

set. This database consists of several sets of configuration data and

parameters, each dedicated to a DP-Slave station. This set of data contains all

necessary information (for the DP-system) to describe a DP-Slave. Additionally,

the master parameter set includes the bus parameters as well as the address-

assignment-table which assigns each individual remote I/O byte an unique address

in the I/O space of the DP-Master's user.

If there exists a valid master parameter set in a DP-Master (class 1), this

device starts to check whether the DP-Slaves dedicated to that DP-Master are

present or not. After an appropriate answer the DP-Master will set the

parameters and check the configuration of that DP-Slave. A DP-Slave will accept

a check configuration request only from the Master who sets the parameters.

After submitting these two functions correctly, a DP-Master checks the status of

the DP-Slave by reading the diagnostic-data. If the configuration check was

successful and parametrization was correct, the DP-Master will enter the user

data exchange mode.

A DP-Slave accepts data exchange requests only from the DP-Master which has

previously submitted parameters and configuration.

A DP-Master (class 1) can send new parameter data to a DP-Slave without leaving

the user data exchange mode.

Additionally, every DP-Master (class 2) can read diagnostic, inputs and outputs

of every DP-Slave.

If there occurred a diagnostic event in the application process of a DP-Slave,

this event is signalled by sending a response with high priority. The DP-Master

has to read the diagnostics and to inform its local user.

A DP-Master (class 2) can take a DP-Slave under its control. In this case the

DP-Slave will stop the data exchange with the DP-Master (class 1). The DP-Master

(class 1) will recognize that and starts to read the diagnostics cyclically. It

checks the field "Master-address" as long as there is a value not equal to

invalid. If the DP-Master (class 2) has finished its communication with that DP-

Slave, it will set the field "Master-address" to invalid. This event triggers

the DP-Master (class 1) to gain control again. As described above it will send

parameters and configuration first.

6.2 Synchronisation

The PROFIBUS-DP system has the capability to synchronize input- and output-data.

These control commands are sent by means of the function Global_Control from a

DP-Master to one, a group of, or all DP-Slaves simultaneously.

With each freeze control command the addressed DP-Slaves read their inputs into

special input buffers. If a read command is issued by a DP-Master, the DP-Slave

will send back the "frozen" input buffers ignoring any change in the recent

past.

With each Sync control command the previously transmitted output values (see

Data_Exchange) will be transferred to the output ports. The output values

transferred with the following Data_Exchange functions will be stored and not

transferred to the output ports till the next Sync control command follows or

the Sync-Mode will be switched off.

Page 702

PROFIBUS-Specification-Normative-Parts-8:1997

The DP-Master (class 1) sends information about his own operation mode to his

dedicated DP-Slaves for synchronisation. This will be done at every change of

the operation mode of the DP-Master (class 1) or occures in time intervals wich

can be parametrized.

6.3 Combination Devices

Besides the types of devices defined in section "Behaviour of the System", it is

possible to build the following functional combination of devices:

- combination of DP-Master (class 1) and DP-Master (class 2)

- combination of DP-Master and FMS-Master

- combination of DP-Slave and FMS-Slave

- DP-Slave with DP-Master (class 1) responder functionality refered

to DDLM- and User-Interface functions

Page 703

PROFIBUS-Specification-Normative-Parts-8:1997

7 Communication Model

7.1 General

PROFIBUS-DP not only describes communication functions, but also a fixed DP

application. According to the ISO communication model, this functionality is

placed in the user-interface. This DP application depends on the device-class

(DP-Master (class 1), DP-Master (class 2) and DP-Slave). For efficiency reasons

the DP-protocoll has no application layer (layer 7, application layer).

PROFIBUS-DP uses only the data transfer services of FDL and FMA1/2 as defined in

PROFIBUS.

To offer a more comfortable layer 2-access, the user needs a direct data link

mapper (DDLM) with predefined DP communication functions.

7.2 Protocol Architecture

This section describes PROFIBUS-DP in the environment of the ISO/OSI basic

reference model, see DIN ISO 7498.

+-------------------------------------+

! !

! User Interface/User !

+-------------------------------------+

! Direct Data Link Mapper !

! (DDLM) !

------------------ +-------------------------------------+

! !

Layer ! empty !

3,4,5,6,7 ! !

------------------ +--------------------------+----------+

! ! !

Layer ! FDL ! !

2 ! ! !

------------------ +--------------------------+FMA 1/2 !

! ! !

Layer ! PHY ! !

1 ! ! !

------------------ +--------------------------+----------+

Figure 1. PROFIBUS-DP Layer Model

Page 704

PROFIBUS-Specification-Normative-Parts-8:1997

DP-Master DP-Master DP-Slave

(class 2) (class 1)

+---------------+ +--------------------+ +---------------+

! ! ! +-----------+ ! ! !

! User ! ! ! User ! ! ! User !

! ! ! ! +---v---+ ! ! !

! ! ! ! +-+-------+-+ !...............!

! ! ! ! ! User ! ! User Interface!

! ! ! ! ! Interface ! ! !

! V V ! ! ! ! V ! ! ∧ ∧ !

+--!--------!---+ +--!-----+------!----+ +--!--------!---+

! ! ! ! ! ! ! ! ! ! ! !

! ! DDLM ! ! ! ! DDLM ! ! ! ! DDLM ! !

! ! ! ! ! ! ! ! ! ! ! !

+--!--------!---+ +--!------------!----+ +--!--------!---+

! ! ! ! ! ! ! ! ! ! ! !

!FDL and FMA1/2! ! !FDL and FMA1/2 ! !FDL and FMA1/2!

! ! ! ! ! ! ! ! ! ! ! !

+--!--------!---+ +--!------------!----+ +--!--------!---+

! ! ! ! ! ! ! ! ! ! ! !

! ! PHY ! ! ! ! PHY ! ! ! ! PHY ! !

! ! ! ! ! ! ! ! ! ! ! !

+--!--------!---+ +--!------------!----+ +--!--------!---+

! ! ! ! ! !

! +------------+ +-------------+ !

+---------------------------------------------------------+

Figure 2. Communication Model

The application (user) of both DP-Master (class 1) and DP-Slave (e. g. PLC as

Master and remote I/O as Slave) communicate via the User-Interface by using

predefined DP applications.

The User-Interface of a DP-Master (class 1) implements the following Master-

Slave application functions:

- read diagnostic information of DP-Slaves

- cyclic user data exchange mode

- parametrization and configuration checking

- submit control commands.

These functions are processed user independent. The interface between user and

User-Interface consists of several service calls and a shared database.

Between a DP-Slave and a DP-Master (class 2) the following functions can be

implemented additionally:

- read configuration of a DP-Slave

- read Input/Output-values

- address-assignment to DP-Slaves

Page 705

PROFIBUS-Specification-Normative-Parts-8:1997

A DP-Master (class 2) invokes the following functions of a DP-Master (class 1):

- read the DP-Master's (class 1) diagnostic

information of the associated DP-Slaves

- upload and download of parameters

- activate bus parameters

- activate and deactivate DP-Slaves

- select the operating mode of a DP-Master (class 1).

These functions are processed by the user of a DP-Master (class 1).

The DDLM offers for the user or the user-interface in all three types of devices

a comfortable access to the PROFIBUS Layer 2.

7.3 Communication Relationships

There are two types of communication in PROFIBUS-DP:

- one-to-one

- one-to-many (Multicast)

The communication depends on the kind of media access of the different stations:

- Master-Slave communication

between DP-Master (class 1) and DP-Slaves

between DP-Master (class 2) and DP-Slaves

- Master-Master communication

between DP-Master (class 2) and DP-Master (class 1)

All types of communications operate connectionless.

In a PROFIBUS-DP system the initiator of a communication request (function) is

always called the requester and the destination station is called the responder

or receiver.

The initiator of a Master-Slave communication is always a DP-Master. The

initiator of a Master-Master communication is always a DP-Master (class 2). No

communication is defined between DP-Masters of the same class.

The figures 3 till 6 give an overview of the allowed types of communication.

All Master-Slave types of communication with the exception of

DDLM_Global_Control are one-to-one communications.

Requester Responder

+----------+ Function.req +---------+

! DP-Master! ---------------> !DP-Slave !

!(class 1)/! ! !

!(class 2) ! <--------------- ! !

+----------+ Function.con +---------+

Figure 3. Master-Slave communication, one-to-one

The Master-Slave communication function DDLM_Global_Control is a Multicast

communication. It is submitted from a DP-Master (class 1 or class 2) to

associated DP-Slaves. This association was made during parametrization of the

DP-Slave. Layer 2 access protection is activated at the beginning of the user

Page 706

PROFIBUS-Specification-Normative-Parts-8:1997

data exchange mode. DP-Slaves which are associated to a DP-Master can be devided

into groups. Groups can be formed by using the group selector.

Requester Receiver

+----------+ Global_Contol.req +---------+

! DP-Master! -------+----------> !DP-Slave !

!(class 2)/! ! ! (1) !

!(class 1) ! ! ! !

+----------+ ! +---------+

! Receiver

! +---------+

! !DP-Slave !

+----------> ! (2) !

! ! !

! +---------+

!

! +---------+

! !DP-Slave !This DP-Slave

! ! (3) ! is not associated

! ! ! to the DP-Master

! +---------+

!

! Receiver

! +---------+

! !DP-Slave !

+----------> ! (4) !

! !

+---------+

Figure 4. Master-Slave communication , one-to-many, Function

DDLM_Global_Control

All Master-Master communication functions are mapped to a one-to-one

communication.

Requester Responder

+---------+ Function.req +---------+

!DP-Master! ---------------> !DP-Master!

!(class 2)! !(class 1)!

! ! <--------------- ! !

+---------+ Function.con +---------+

Figure 5. Master-Master communication, one-to-one

The Master-Master communication function DDLM_Act_Para_Brct can additionally

mapped as a one-to-many communication.

Page 707

PROFIBUS-Specification-Normative-Parts-8:1997

Requester Receiver

+---------+Act_Para_Brct.req +---------+

!DP-Master! -------+-------> !DP-Master!

!(class 2)! ! !(class 1)!

! ! ! ! !

+---------+ ! +---------+

! Receiver

! +---------+

! !DP-Master!

+------> !(class 1)!

! ! !

! +---------+

!

! +---------+

! !DP-Master!

! !(class 2)!

! ! !

! +---------+

!

! Receiver

! +---------+

! !DP-Master!

+------> !(class 1)!

! !

+---------+

Figure 6. Master-Master communication, one-to-many, Function

DDLM_Act_Para_Brct

7.4 Overview of Functions

PROFIBUS-DP offers the following basic functions:

- Master-Diagnostic read

Via this function a DP-Master's (class 1) diagnostic information about its

associated DP-Slaves can be read. The diagnostic information consists of a

global diagnostic overview and station diagnostics. A parameter switch selects

the requested functionality.

- Parameter Up-/Download

These functions allow the transfer of parameter sets between two DP-Masters.

Special parameter sets are for Example the bus parameters and the DP-Slave

parameters. The second one is needed to set parameters and check the

configuration of an associated DP-Slave.

- Activate bus parameter

This function activates a previously loaded set of bus parameter.

Page 708

PROFIBUS-Specification-Normative-Parts-8:1997

- Activate/Deactivate DP-Slaves

With this function a DP-Master can be forced to stop polling the DP-Slave or to

start again to poll a DP-Slave.

- DP-Slave-Diagnostic information read

An application can read diagnostic information from a DP-Slave with this

function.

- Data exchange of the inputs/outputs

This function is used for cyclic I/O-Data exchange between DP-Master (class 1)

and associated DP-Slaves. The number of inputs and outputs is defined in the

configuration data at startup of the DP-System.

- Set parameters of the DP-Slave

This function sets the parameters of the DP-Slaves at system startup, after a

restart and in the user data exchange mode of a DP-System. There are some

parameters that are unique in all DP-Slaves, the others are specific for each

station.

- Check configuration of a DP-Slave

With this function the DP-Slave can check the configuration. The main purpose is

to define the number and structure of inputs and outputs.

- Send control commands to DP-Slaves

A Master can send special control commands to one (single) or several

(multicast) DP-Slaves. Different commands are distinguished by a parameter.

- Read configuration data of a DP-Slave

If a master has no configuration data of a DP-Slave it can read this information

by means of that function.

- Read inputs and outputs of DP-Slaves

This function enables all DP-Masters to read the inputs and outputs of a DP-

Slave while it is under control of a specific master.

- Change station address of a DP-Slave

The station-address can be set by a DP-Master during initialization.

Page 709

PROFIBUS-Specification-Normative-Parts-8:1997

7.5 Service Execution

This section shows the processing of PROFIBUS-DP functions according to well

established description techniques. A function consists of a set of primitives.

The primitives are adapted to the DP-Protocol architecture.

All DDLM functions are executed sequentially in a fixed order. Parallel or

concurrent function requests are not allowed.

7.5.1 Master-Slave Communication

Communication requests are initiated at the User-Interface of a Master and will

be sent to the DDLM by means of the function primitive Request (.req). The DDLM

Acknowledgement will be received using the function-primitive (.con).

Depending on the type of DDLM function, four sequences of processing can be

identified between User/User-Interface, DDLM and PROFIBUS layer 2. All Master-

Slave communication functions are executed in one layer 2 message cycle

(immediate response). This means that the data which has to be read of the DP-

Slave will not be transferred with an indication-response sequence, but in

advance with an Upd.req-primitive to layer 2.

The coding of the DDLM functions is implicit by using a defined set of layer 2

service access points. This coding information is sufficient for the DDLM in the

case of Master-Slave communication.

The definitions of the possible Master-Slave functions can be found in section

"DP-Master - DP-Slave Functions".

User- User-

Interface ! DDLM !FDL BUS FDL! DDLM ! Interface

----------------------------------------------------------------

! ! ! !

! ! ! !Function_Upd.req

! ! !Upd.req !<---------

! ! (--!<--------!

! ! (->!-->] !

! ! !Upd.con !

! ! ! !

Function.req ! ! ! !

------------>! SRD.req !(Data/no Data)! !

!-------->! SRD_REQ_PDU ! !

! !------------->!SRD.ind !

! !<------------/!-------->!Function.ind

!<--------! SRD_RES_PDU ! !----------->

<------------! SRD.con ! (Data) ! !

Function.con ! ! ! !

! ! ! !

Figure 7. Processing of Master-Slave communication of the DDLM_functions

DDLM_Data_Exchange and DDLM_Slave_Diag

Page 710

PROFIBUS-Specification-Normative-Parts-8:1997

User ! DDLM !FDL BUS FDL! DDLM ! User

----------------------------------------------------------------

! ! ! !

! ! ! !Function_Upd.req

! ! !Upd.req !<---------

! ! (--!<--------!

! ! (->!-->] !

! ! !Upd.con !

! ! ! !

Function.req ! ! ! !

------------>! SRD.req ! (no Data) ! !

!-------->! SRD_REQ_PDU !SRD.ind !

! !------------->!--->] !

! !<------------/! !

!<--------! SRD_RES_PDU ! !

<------------! SRD.con ! (Data) ! !

Function.con ! ! ! !

! ! ! !

Figure 8. Processing of Master-Slave communication of the DDLM_functions

RD_Inp, RD_Outp and Get_Cfg

User- User-

Interface ! DDLM !FDL BUS FDL! DDLM ! Interface

-----------------------------------------------------------

! ! ! !

Function.req ! ! ! !

------------>! SRD.req ! (Data) ! !

!-------->! SRD_REQ_PDU ! !

! !------------->!SRD.ind !

! !<------------/!-------->!Function.ind

!<--------! SRD_RES_PDU ! !----------->

<------------! SRD.con ! (no Data) ! !

Function.con ! ! ! !

! ! ! !

Figure 9. Processing of Master-Slave communication of the DDLM_functions

Set_Prm, Chk_Cfg and Set_Slave_Add

Спецификация протокола Profibus

Подождите немного. Документ загружается.