Спецификация протокола Profibus
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Table 30. Additional FDL Variables
+------------+------------------------------------------------+
! Name ! Meaning !
+------------+------------------------------------------------+
! T
RR
*) ! Real Rotation Time !
! ! !
! LAS *) ! List of Master Stations in the logical ring !
! GAPL *) ! List all of Stations in the own GAP !
+------------+------------------------------------------------+
! *) only possible in Master Stations !
+-------------------------------------------------------------+
FDL_READ_VALUE.confirm
(Current_value)
- The parameter Current_value contains the current value of the variable which
was specified in the preceding FDL_READ_VALUE.request primitive. In addition
to the ranges of values defined for the FDL_SET_VALUE.request primitive (see
Table 29) the following ranges are permissible for the variables and the
counters above:
Table 31. Values of the additional FDL Variables
+------------------+------------------------------------------+
! Variable ! Range !
+------------------+------------------------------------------+
! T
RR
! 2
0
to 2
24
-1 (Bit Times) !
! ! !
! LAS ! preferably maximum 32 FDL addresses !
! ! (0 to 126), optionally up to 127 FDL !
! ! addresses !
! GAPL ! max. 126 FDL addresses (0 to 126) !
! ! inclusive FDL Status !
+==================+==========================================+
! Counters (optional) !
+------------------+------------------------------------------+
! Variable ! Range !
+------------------+------------------------------------------+
! Frame_sent_count ! 0 to 2
32
-1 !
! Retry_count ! 0 to 2
16
-1 !
! ! !
! SD_count ! 0 to 2
32
-1 !
! SD_error_count ! 0 to 2
16
-1 !
+------------------+------------------------------------------+
5.2.3.3 Fault FDL
The service "Fault FDL" is mandatory.
The FDL controller delivers a FDL_FAULT.indication primitive to the FMA1/2 to
inform FMA1/2 that it has detected a faulty condition or an event.
Parameters of the Primitives
FDL_FAULT.indication
(Fault_type)
- The parameter Fault_type gives the following error reasons:
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Table 32. FDL Error Reasons
+----------------------+--------------------------------------+
! Name ! Meaning !
+----------------------+--------------------------------------+
! Duplicate_address *)! A duplicate of this station's FDL !
! ! address exists. !
! Faulty_transceiver *)! The Transmitter or Receiver of this !
! ! station is malfunctioning !
! Time_out ! No bus activity !
! Not_syn ! Synchronization not detected within !
! ! Syn-Interval-Time T
SYNI
!
! Out_of_ring *)! This Master Station was taken from !
! ! the logical ring not on its own !
! ! initiative !
! GAP_event *)! A change in the GAPL has occurred !
+----------------------+--------------------------------------+
! *) only possible in Master Stations !
+-------------------------------------------------------------+
5.3 PHY - FMA1/2 Interface
User
----------- +---------------------+---------+
! ! !
Layer 2 ! FDL ! !
! ! !
----------- +---------------------+
FMA1/2
!
!
I
!
Layer 1 !
PHY I
!
!
I
!
----------- +--------+---+--------+---------+
---------+ +-------------------
"Layer 0" Physical Media
---------------------------------
Figure 13. Interface between PHY and FMA1/2 in Relation to Layer Model
5.3.1 Overview of Services
The PHY Layer offers the following services to FMA1/2:
- Reset PHY
- Set Value PHY
- Read Value PHY
- Event PHY
Reset PHY (mandatory)
This service allows the FMA1/2 to reset the PHY Layer directly. The management
receives a confirmation.
Set Value PHY (optional)
With this service the FMA1/2 is able to set certain variables in the PHY. PHY
gives a confirmation to the FMA1/2 as to whether the variable could take the
desired value.
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Read Value PHY (optional)
With this service the FMA1/2 is able to read certain variables of the PHY. In
the response the current value of the selected variable is transferred to the
FMA1/2.
Event PHY (optional)
The PHY uses this service to inform the FMA1/2 about the changes in value of
certain variables.
5.3.2 Overview of Interactions
The services mentioned in subclause 5.3.1 are described by following primitives
(PHY_...):
Service Primitive permissible for
following users
Reset PHY PHY_RESET.request Master and Slave
PHY_RESET.confirm - " -
Set Value PHY PHY_SET_VALUE.request Master and Slave
PHY_SET_VALUE.confirm - " -
Read Value PHY PHY_READ_VALUE.request Master and Slave
PHY_READ_VALUE.confirm - " -
Event PHY PHY_EVENT.indication Master and Slave
Temporal Relationships of Service Primitives:
Master/Slave Master/Slave
Station 1 Station n
FMA1/2
!
PHY
! !
! ! !
PHY_XXXXX.req ! ! !
-------------->!-- ! !
! ) ! !
PHY_XXXXX.con ! ) ! !
<--------------!<- ! !
! ! !
Figure 14. Reset PHY, Set Value PHY, Read Value PHY Service
Master/Slave Master/Slave
Station 1 Station n
FMA1/2
!
PHY
! !
! ! !
! ! !
PHY_EVENT.ind ! ! !
<--------------!-- ! !
! ! !
Figure 15. Event PHY Service
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5.3.3 Detailed Specification of Services and Interactions
5.3.3.1 Reset PHY
The service "Reset PHY" is mandatory.
The PHY_RESET.request primitive is given to the PHY by the FMA1/2 to reset PHY.
The PHY executes this in exactly the same manner as at a Power On (Transmitter_
output: enable; Receiver_signal_source: primary; Loop: disable). An immediately
returned PHY_RESET.confirm primitive informs the FMA1/2 of the executed reset.
Parameters of the Primitives:
PHY_RESET.request
PHY_RESET.confirm
- Both primitives have no parameters.
5.3.3.2 Set Value PHY, Read Value PHY
Set Value PHY
The service "Set Value PHY" is optional.
The FMA1/2 delivers a PHY_SET_VALUE.request primitive to the PHY to set a speci-
fied variable to a desired value. After receiving the primitive the PHY selects
the variable and sets it to the value. The FMA1/2 receives a confirmation in a
PHY_SET_VALUE.confirm primitive.
Parameters of the Primitives
PHY_SET_VALUE.request
(Variable_name, Desired_value)
- The parameter Variable_name specifies the following variables:
Table 33. PHY Variables (Set Value)
+------------------------+------------------------------------+
! Name ! Meaning !
+------------------------+------------------------------------+
! Transmitter_output ! Transmitter Output !
! Received_signal_source ! Receiver Input !
! Loop ! The Transmitter Output is directed !
! ! to the Receiver Input and not to !
! ! the Medium !
+------------------------+------------------------------------+
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- The parameter Desired_value specifies the new value for the variable:
Table 34. Values of PHY Variables (Set Value)
+------------------------+---------------------------------------------+
! Variable ! Values !
+------------------------+---------------------------------------------+
! Transmitter_output ! enabled (indirect); disabled !
! Received_signal_source ! primary (standard source = Bus a) !
! ! alternate (alternative source = !
! ! Bus b),(see Part 2, clause 4.3) !
! ! random (either Bus a or Bus b) !
! Loop ! enabled; disabled !
+------------------------+---------------------------------------------+
PHY_SET_VALUE.confirm
- This primitive has no parameters.
Read Value PHY
The service "Read Value PHY" is optional.
The FMA1/2 delivers a PHY_READ_VALUE.request primitive to the PHY to read a
specified variable. The PHY transfers the value of the variable in a PHY_READ_
VALUE.confirm primitive to the FMA1/2.
Parameters of the Primitives
PHY_READ_VALUE.request
(Variable_name)
- The parameter Variable_name specifies the following variables:
Table 35. PHY Variables (Read Value)
+------------------------+------------------------------------+
! Name ! Meaning !
+------------------------+------------------------------------+
! Transmitter_output ! Transmitter Output !
! Received_signal_source ! Receiver Input !
! Loop ! internal Send Receive Loop !
+------------------------+------------------------------------+
PHY_READ_VALUE.confirm
(Current_value)
- The parameter Current_value contains the current value which was requested
with the preceding PHY_READ_VALUE.request primitive. The following values are
permitted for the variables:
Table 36. Value of PHY Variables (Read Value)
+------------------------+---------------------+
! Variable ! Values !
+------------------------+---------------------+
! Transmitter_output ! enabled; disabled !
! Received_signal_source ! primary; alternate !
! Loop ! enabled; disabled !
+------------------------+---------------------+
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5.3.3.3 Event PHY
The service "Event PHY" is optional.
The PHY uses this service to inform the FMA1/2 that a variable value was
changed.
Parameters of the Primitives
PHY_EVENT.indication
(Variable_name, New_value)
- The parameter Variable_name specifies the variable whose value was changed:
Table 37. PHY Variables (Event)
+-------------------------+---------------------+
! Name ! Meaning !
+-------------------------+---------------------+
! Transmitter_output ! Transmitter Output !
! Received_signal_source ! Receiver Input !
+-------------------------+---------------------+
- The parameter New_value specifies the new value of the variable.
Table 38. Values of PHY Variables (Event)
+-------------------------+--------------------+
! Variable ! Values !
+-------------------------+--------------------+
! Transmitter_output ! disabled; enabled !
! Received_signal_source ! primary; alternate !
+-------------------------+--------------------+
Page 97
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PROFIBUS Specification - Normative Parts
Part 4
Data Link Layer Protocol Specification
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Contents
Page
1 Scope ...............................................................99
2 Normative References ................................................99
3 General .............................................................99
4 Medium Access Methods and Transmission Protocol (Data Link
Layer, FDL) .........................................................99
4.1 Transmission Procedures and FDL Controller ..........................99
4.1.1 Token Procedures ...................................................100
4.1.1.1 Token Passing ......................................................100
4.1.1.2 Addition and Removal of Stations ...................................101
4.1.1.3 (Re)Initializing the Logical Token Ring ............................102
4.1.1.4 Token Rotation Time ................................................103
4.1.1.5 Message Priorities .................................................104
4.1.2 Acyclic Request or Send/Request Mode ...............................104
4.1.3 Cyclic Send/Request Mode ...........................................104
4.1.4 Request FDL Status of all Stations (Live List) .....................105
4.1.5 Status of the FDL Controller .......................................106
4.1.6 FDL Initialization .................................................110
4.1.7 Timer Operation ....................................................111
4.2 Cycle and System Reaction Times ....................................116
4.2.1 Token Cycle Time ...................................................116
4.2.2 Message Cycle Time .................................................117
4.2.3 System Reaction Times ..............................................118
4.3 Error Control Procedures ...........................................118
4.4 Timers and Counters ................................................119
4.5 Frame Structure ....................................................121
4.5.1 Frame Character (UART Character) ...................................121
4.5.2 Bit Synchronizing ..................................................121
4.6 Frame Formats ......................................................121
4.6.1 Frames of fixed Length with no Data Field ..........................122
4.6.2 Frames of fixed Length with Data Field .............................123
4.6.3 Frames with variable Data Field Length .............................124
4.6.4 Token Frame ........................................................125
4.7 Length, Address, Control and Check Octet ...........................125
4.7.1 Length Octet (LE, LEr) .............................................125
4.7.2 Address Octet (DA/SA) ..............................................126
4.7.2.1 Address Check ......................................................128
4.7.2.2 Link Service Access Point (LSAP) ...................................128
4.7.3 Control Octet (FC) .................................................129
4.7.4 Check Octet (FCS) ..................................................132
4.7.5 Data Field (DATA_UNIT) .............................................133
4.8 Transmission Procedures ............................................136
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1 Scope
(see Part 2)
2 Normative References
(see Part 2)
3 General
(see Part 2)
4 Medium Access Methods and Transmission Protocol (Data Link Layer, FDL)
A PROFIBUS System uses controlled medium access accomplished by a hybrid medium
access method: a decentral method according to the principle of Token Passing is
underlain by a central method according to the Master - Slave principle. Medium
access control may be exercised by each master station (active station). Slave
stations (passive stations) act neutrally in respect to medium access, i.e. they
do not transmit independently but only on request.
Communication is always initiated by the master station which has the permission
for medium access, the token. The token is passed from master station to master
station in a logical ring and thus determines the instant, when a master station
may access the medium. Controlled token passing is managed by each station know-
ing its predecessor (Previous Station, PS), the station from which it receives
the token. Furthermore each station knows its successor (Next Station, NS), i.e.
the station to which the token is transmitted, and its own address (This Sta-
tion, TS). Each master station determines the PS and NS addresses after the
initialization of the operating parameters for the first time and then later
dynamically according to the algorithm described in subclause 4.1.1.2.
If the logical ring consists of only one master and several slave stations then
it is a pure master - slave system.
The following error conditions, exceptions and operational states in the system
are dealt with:
1) multiple tokens
2) lost token
3) error in token passing
4) duplicate station addresses
5) stations with faulty transmitter/receiver
6) adding and removing stations during operation
7) any combinations of master and slave stations
4.1 Transmission Procedures and FDL Controller
The exchange of messages takes place in cycles. A message cycle consists of a
master station's action frame (request or send/request frame) and the associated
acknowledgement or response frame of a master or a slave station. User data may
be transmitted in the action frame (send) as well as in the response frame
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(response). The acknowledgement frame does not contain any user data (for frame
formats see clause 4.6).
The complete message cycle is only interrupted for token transmission and for
the transmission of data without acknowledgement (e.g. necessary for broadcast
messages). In both modes of operation there is no acknowledgement. In broadcast
messages a master station (initiator) addresses all other stations at the same
time by means of a global address (highest station address, all address bits
binary "1").
All stations except the respective token holder (initiator) shall in general
monitor all requests. The stations acknowledge or respond only when they are ad-
dressed. The acknowledgement or response shall arrive within a predefined time,
the Slot Time, otherwise the initiator repeats the request if it is not a "first
request" (see subclause 4.7.3, FCB). A retry or a new request shall not be
issued by the initiator before the expiration of a waiting period, the Idle Time
(see subclause 4.1.7).
If the responder does not acknowledge or respond after a predefined number of
retries (see subclause 4.1.6), it is marked as "non-operational". If a responder
is "non-operational", a later unsuccessful request will not be repeated.
The modes of transmission operation define the time sequence of the message
cycles. Four types are distinguished:
1) Token handling
2) Acyclic request or send/request operation
3) Cyclic send/request operation, polling
4) Registration of stations
4.1.1 Token Procedures
4.1.1.1 Token Passing
The token is passed from master station to master station in ascending numerical
order of station addresses by means of the token frame (see subclause 4.6.4).
The one exception is that, to close the logical token ring, the station with the
highest address passes the token to the station with the lowest address (see
Fig.1).
Token Reception:
If a master station (TS) receives a token frame addressed to itself from a sta-
tion which is registered as Previous Station (PS) in its List of Active Stations
(LAS), it owns the token and may execute message cycles. The LAS is generated in
the master station in the "Listen_Token" state (see subclause 4.1.5) after power
on and updated and corrected, if necessary, later on upon receipt of a token
frame.
If the token transmitter is not the registered PS, the addressee shall assume an
error and not accept the token. Only a subsequent retry of the same PS is ac-
cepted and results in the token receipt, because the token receiver shall assume
now that the logical ring has changed. It replaces the originally recorded PS in
its LAS by the new one.