Transcript Document 7695922

Train Communication Network
IEC 61375-2
Real Time Protocols
Message Services
IEC Train Communication Network
Real-Time Protocols
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1999 December, HK
IEC 61375 - Clause 2
RTP- Message Services
1. General Principles
2. Variables
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Varialbles
6. Networking
3. Messages
1. Principle of Message Data communication
2. Link Layer Interface
3. Networking and Routing
4. Transport protocol
5. Software structure
6. Application Interface
IEC Train Communication Network
Real-Time Protocols
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IEC 61375 - Clause 2
urgent
less urgent
variables
messages
presentation
presentation
Layer
Management
(session)
void
(transport)
(network)
Protocols
Layer 7 interface
Network-independent
TCN Stack
periodic
medium access
sporadic
medium access
process data
message data
supervisory
access
supervisory data
Link
Layer 2 interface
Layer 1 interface
physical signalling
physical media
Physical
medium-independent signalling
mechanical and electrical elements
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Real-Time Protocols
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IEC 61375 - Clause 2
Functions and Devices
Each vehicle supports a number of standardized functions.
The Train Bus accesses vehicles without knowing their internal structure.
The train bus accesses functions rather thandevices.
These functions are implemented by one or several vehicle bus devices,
or even by the gateway itself.
Train Bus
bus
master
sensors/
actors
device
doors
train-vehicle
gateway
air condition
passenger info
device
device
device
sensor bus
vehicle
bus
device
doors
brakes
The gateway deduces the device from the function and routes messages.
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Real-Time Protocols
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Client-Server Service
Caller
Transport
Network
Transport
Replier
Receive_Request
Call_Request
Receive_Confirm
replier
time-out
Reply_Request
Call_Confirm
Receive_Request
time
The Application Interface for Messages provides a "Call with Reply" service
Applications communicate among themselves on a Client/Server basis.
Tasks use the same communication scheme:
• within the same processor
• within the same vehicle bus and
• within the Train Communication Network
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Real-Time Protocols
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IEC 61375 - Clause 2
Transport Protocol for Messages
The transport protocol ensures a reliable communication from end-to-end
between Application Functions.
train bus
gateway
F
F
gateway vehicle
bus
vehicle
bus
F
the message transport
protocol is executed by
the vehicle bus devices
F
F
F
F
F
the message transport
protocol applies also within
the same bus and within
the same device.
node
functions
F
F
F
F
F
in vehicles without vehicle bus,
the message transport protocol
is executed by the train bus
node
The Message Transport Protocol runs in each device
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Real-Time Protocols
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Message Data Transmission
Messages are lengthy, but not so urgent data.
They are used e.g. for diagnostics, passenger information, down-loading.
Messages are segmented into packets for transmission.
Data, ackowledgements and control packets form theMessage Data.
Message Data are sent upon demand between two process data cycles.
The sender and receivers of Message Data are queues (no buffers):
Application Processes
send
queue
receive
queue
Bus
acknowledgements
data packets
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Real-Time Protocols
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End-to-end Transport Protocol
(router)
(router)
application
application
application
application
presentation
presentation
presentation
presentation
session
session
session
session
transport
transport
transport
transport
network
network
network
network
Message
Transport
Protocol
link
link
link
link
link
link
physical
physical
physical
physical
physical
physical
MVB segment
WTB segment
MVB segment
Porting the MTP to a bus providing connectionless datagrams is easy
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Real-Time Protocols
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RTP- Network Layer
1. General Principles
2. Process Data
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
3. Messages
1. Principle of Messages communication
2. Link Layer Interface
3. Networking and Routing
4. Transport and Session protocol
5. Software structure
6. Application Interface
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Real-Time Protocols
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Network: Packet Routing
The gateway operates as arouter : it forwards packets from bus to bus
without keeping knowledge of previous packets.
Packets are transported in Message Data frames as datagrams
which contain the full origin and final address.
Message Data frame
net_adr
train bus
source
destination
gateway
gateway
gateway
net_adr
source
net_adr
destination
origin
station
final
station
source
destination
vehicle bus
IEC Train Communication Network
Real-Time Protocols
gateway
vehicle bus
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Network: Message Data Frames
Message Data carry data packets, acknowledgements and control data.
network
addresses
link header
WTB
DD LLC
4
DD
12
type
MVB
mode
8 bits 8
4
SD size
8
8
SD size
12
8
DD: destination device
SD: source device
LLC: link layer control
MTC: Messsage Transport Control
final
origin
8
8
8
8
final
origin
8
8
8
MTC
transport data unit
8
MTC
8
transport data unit
8
Link Data Unit - common to all busses
Message Data have the same format on the vehicle or on the train bus.
They are datagrams, which carry the full origin and final address
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Real-Time Protocols
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Networking Different Busses
node
gateway
vehicle bus
gateway
vehicle bus
train levelbus
backplane
stations
sensor bus
sensors &
actuators
2-level hierarchy
Intelligent stations and
sensors/actuators are
attached to the vehicle bus
3-level hierachy
Sensors are attached
directly or by a sensor
bus
1-level hierarchy
Equipments are attached
to a node-internal
backplane bus which plays
the role of a vehicle bus
The real-time protocols allow to interconnect different vehicle structures
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Real-Time Protocols
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Network Layer Operation
The network layer is responsible for the routing of packets
(data, acknowledgement and control) through the network
Routing relies on the network addresses contained in each packet.
It is connectionless, i.e. it retains no knowledge about previous packets
belonging to the same message
Routing is done on the base of two directory tables:
• station directory
• function directory
These directories are set up by the application or by network management.
The network layer has no protocols (no segmentation / reassembly), but
address calculation is complex.
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Real-Time Protocols
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Network: Reference Architecture
Train Bus
UPf
LL
LL
station
Agent
UP1
UP2
station
UPf
Application
Processes
LL
messenger
Agent
UP1
UP2
messenger
UP2
UPf
messenger
UPf
LL
messenger
UP2
Agent
UP1
router
LL
Vehicle Bus
LL
Agent
UP1
node
User Processes
LL
Vehicle Bus
LL
messenger
router
messenger
LL
link layer
node
messenger
node
Agent
UP1
UP2
UPf
Agent
UP1
UP2
UPf
Agent
UP1
UP2
UPf
All Application Processes (UPs, Agents) communicate through the Messenger.
A station is a (vehicle or train bus) device capable of message communication.
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Network: Example of an Actual Configuration
Train Bus
node 05 #001
node 06
UPf
UP1
UP2
UPf
0020 0020
#002
Station Identifier
56
#102
0022
#123
0023
#157
57
Agent
#103
#125
#158
Manager
0023
0025
58
#004 (Station Identifier)
messenger
Vehicle Bus
UPf
#156
56
Vehicle Busses
UP1
UPf
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Real-Time Protocols
UP2
#122
0022
Physical Address
#003
0003
UP1
#101
0021
0002
repeater
messenger
UP2
#001
Agent
router
UP1
0001
0004
(physical
address)
node 07
Agent
messenger
messenger
router
Agent
#011
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Network: Reference Gateway
User
User
User
Processes
Processes
Processes
Application
Processes
Agent
Application Layer
Session Layer
application interface AM
Message Transport Protocol
FunDi
Messenger
NodDi
LM
WTB
Link Layer
WTB physical medium
Router
LM
Transport Layer
Network Layer
StaDi
MVB
Link Layer
MVB physical medium
Link Layer
Physical Layer
Agent = Station Management Agent
(for parametrizing, down-loading, configuration, debugging, performance measurement)
A gateway has a router and more than one link layer
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Real-Time Protocols
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Network: System Point Of View
Train Bus
Node # 01
station
(agent)
#002
station
(agent)
#003
Node # 03
Node # 02
station
(agent)
#020
station
(agent)
#001
station
(agent)
#003
station
(agent &
manager)
#100
station
(agent)
#001
The System Engineer identifies stations attached to train bus nodes.
The train bus node counts as one station.
The interconnection of the stations is not visible (no, 1, 2,... vehicle busses).
The communicating entities are the Agents and the Managers.
The nodes route the packets through their Station Directory
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Real-Time Protocols
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Network: Train Bus Addresses
The Train Bus operates with nodes addresses, which is the position of a node
relative to the master node (address 01)
63
01
02
(master)
03
04
05
06
07
08
The train inauguration gives each node its position and the direction of the master.
UIC applications address vehicles by their position relative to the head of the train.
principal direction of travel
01
02
03
04
pushed vehicles
05
06
07
08
hauled vehicles
attended driver's cab
Since a vehicle may have one, two or no operative node, there must exist a
mapping between node address and UIC application address.
The real-time protocols only rely on the TCN addressing.
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Real-Time Protocols
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Network: Example Of Communication
Train Bus
0100
Vehicle
Bus
(Physical)
Address
Node # 06
#001
#002
0002
#103
0003
Station
Identifier
UP1
UP2
UPf
IEC Train Communication Network
Real-Time Protocols
#002
0002
0200
#002
0002
#003
0003
#003
0003
#004
#232
0004
0232
Vehicle Bus
messenger
Vehicle Bus
LL
Agent
Node # 08
Vehicle Bus
Node # 05
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Network: Example of Frame Exchange
physical addresses
simple routing
Forth
VB
origin
0100
TB
intermediate
VB
final
network addresses
08
0133
08
232
(05)
133
application knows that node #8 is
accessed over Station #100
(its gateway)
05
08
232
05
133
node #05 inserts its current node
address
232
05
133
node #8 routes Station #232 to VB
Address 0232 (simple routing)
simple routing
05
133 (08)
232
Station #232 acknowledges to
Station #200.
05
simple routing
0232
0200
(08)
Back
VB
origin
0200
TB
intermediate
VB
final
0133
0232
05
08
simple routing
0100
(05)
IEC Train Communication Network
Real-Time Protocols
133
08
232
node #08 checks
its correct TB address
133
08
232
node #05 routes Station #133 to
VB address 0133 (simple routing)
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Network: Station Directory
The Station Directory in the network layer routes the messages on the base of
their station address to the corresponding link layer and device address
Station
Link Layer
003
MVB1
0003
005
MVB1
0005
103
MVB2
0003
223
Parallel_Bus
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Real-Time Protocols
Physical Address
203040
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Network: Routing Between Two Vehicle Busses
Train Bus
station #001 gateway
bus address 0011
bus address 1011
Vehicle Bus 1
station:
bus address:
Vehicle Bus 2
#002
#003
#004
#005
#006
#007
#008
#009
0012
0013
0014
0015
0012
0013
1014
1015
device group 2
device group 1
Two (or more) vehicle busses may be attached to a train bus gateway.
The gateway routes message data according to the network address
from vehicle bus to vehicle bus or from vehicle bus to train bus.
The station identifier must be unique under a given train bus node.
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Real-Time Protocols
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Network: Sensor Bus Configuration
Train Bus
Station
#001
messenger
StaDi
router
agent
UP1
UP2
UPf
agent
#002
Vehicle Bus
agent
#003
Station
#004
agent
messenger
router
StaDi
UP1
UP2
UPf
Sensor Bus
agent
#100
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Real-Time Protocols
agent
#101
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agent
#102
IEC 61375 - Clause 2
Network: Sensor Bus Path
Train Bus
Node # 08
Node # 05
router
StaDi
0100
#103
Station Directory
0003
Station Identifier
0202
0204
Real-Time Protocols
Station Identifier
VB address
Station #206
agent
Sensor Bus
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SB
1
#292
2
messenger
station link device
#294 SB 4
router
0206
Station Identifier
SB address
IEC Train Communication Network
UPf
StaDi
VB address
Vehicle Bus
0133
UP2
#202
0202
VB
#133
UP1
Station
Identifier
0200
Vehicle Bus
#002
0002
station link device
#206 VB 206
#294 VB 206
messenger
agent
Node # 05
#293
3
UP1
UP2
UPf
#294
4
IEC 61375 - Clause 2
Network: User Point Of View
Train Bus
Node # 01
F1
F2
Node # 02
F3
F1
F2
Node # t
F3
F1
F2
F3
The user sees functions attached to nodes.
The node itself is not a function - but the node device can implement functions
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Real-Time Protocols
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Network: Function Architecture
The communicating entities are functions in the different stations
FunDi
UP2
UPf
messenger
UP1
FunDi
UP1
router
UP1
messenger
UP2
UPf
agent
UP1
UP1
messenger
agent
UP2
UPf
FunDi
agent
FunDi
UP1
UP2
Application
Processes
UPf
UP2
UPf
agent
router
messenger
agent
messenger
FunDi
agent
UPf
messenger
FunDi
FunDi
agent
UP2
messenger
Vehicle Bus
router
Train Bus
UP1
UP2
UPf
Sensor Bus
UP
#100
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Real-Time Protocols
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UP
#101
UP
#102
IEC 61375 - Clause 2
Network: Function Directory
The Function Directory maps the function to the corresponding station
Function Directory
Function
Station
2
003
5
104
7
0 (local)
12
30
Station Directory
Station
003
MVB1
0003
005
MVB1
0005
103
local
0
223
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Real-Time Protocols
Link Layer Physical Address
Parallel_Bus
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203040
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Network: Address Kinds
Physical Address:
identifies a device on a bus - can be a broadcast address.
gateways have more than one physical address
each frame carries the source and destination address.
Link Identifier:
In a gateway, link layers are identified by their
address (e.g. 1,2)
Link Service Access Point
Only one default LSAP is used in TCN (unused).
Network Address:
The application process identifies the remote application
process through its network address.
Each frame carries the origin and final network address
The network address is the concadenation node + (station or function)
Application Address:
All other addresses are deduced from this one.
system/user
1 bit
individual/group
1 bit
node
6 bits
station or function 8 bits
next station
8 bits
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Real-Time Protocols
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Network: Address Calculation
Application Address
train bus node
next station (device)
function (user process)
station (agent)
16-bit Station Address
1
node
(1/254) Station Identifier
1 = System (Station)
16-bit Function Address
0 0/1
node
0 = User (Function)
0 = individual
1 = group
(1/255) Function Identifier
Function
Directory
Station
Station
Directory
Link and Physical Address
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Real-Time Protocols
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Network: Message Consistency and WTB Topography
Transport level:
if a topography change occurs while a message is transmitted,
the remaining packets may be delivered to the wrong node.
Session level:
if a topography change occurs between a call and a reply message,
the reply message may be delivered to the wrong node.
This misaddressing will be detected in most cases.
When nodes swap their addresses, undetectable situations may occur.
When topography changes, each WTB node signals its messenger,
which cancels all ongoing message data communication over the WTB and
flushes the queues of the WTB link layer.
To this effect, each WTB node maintains a topography counter, which is
incremented each time the topography of the WTB changes.
All packets of a message exchanged over the vehicle bus carry the topography
counter in place of the local node address (which is redundant).
If a station detects that topography changed, it cancels only that conversation.
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Real-Time Protocols
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Network: Impact of Topography Change on Communication
A topography change cancels indistinctly all conversations over the WTB.
It would not be necessary to cancel conversations between nodes which
did not change their addresses.
However, it is not possible to guarantee that the topography change did
not affect the addresses of either partner.
Even if no node address changed, it is not possible to guarantee that the
reason why this address was chosen still holds.
Even if the node address and function did not change, the application mapping
may not anymore be correct, since it was based on some dynamic property of
the node which changed in between (e.g. attended driver seat).
Therefore, communication must be cancelled indistinctly when the transport
protocol becomes unable to guarantee correct delivery in all cases.
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Real-Time Protocols
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Network: Inclusion of Topography Counter
Train Bus
"producer"
Node # 05
Vehicle Bus
FN
LTC8
Local
Topography
Counter
ON
producer
station
Final Node
FN
Vehicle Bus
LTC5
ON
"consumer"
node # 08
Node # 06
Origin Node
FN
08
X
00
X
CR
LTC5
X
08
X
CC
08
X
LTC5
X
DT
LTC5
X
08
X
AK
consumer
station
ON
LTC8
X
05
X
CR
05
X
LTC8
X
CC
LTC8
X
05
X
DT
05
X
LTC8
X
AK
The gateway substitutes the topography counter in place of the node address
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Transport and Session Protocol
1. General Principles
2. Variables
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
3. Messages
1. Principle of Messages communication
2. Link Layer Interface
3. Networking and Routing
4. Transport and Session Protocol
5. Software structure
6. Application Interface
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Real-Time Protocols
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Transport: Message Transport Protocol
The MTP opens a connection for each call message and
closes it after the reply message has been received.
It is half-duplex (call and reply cannot take place at the same time)
It uses in each direction a sliding window protocol with a window size of 1…7
and positive acknowledgement (negative is also possible)
The frame and window size are negotiated at connection opening.
The origin and destination addresses uniquely identify the connection.
A connection reference prevents duplication of messages.
A caller reference pairs messages in a multi-tasking station.
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Real-Time Protocols
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Transport: Frame Exchange in one Direction
Session
(Producer)
Transport
Network
Transport
Session
(Consumer)
Connection
tm_message.req
Connect Request
connect
time-out
sm_connect.ind
i
sm_connect.cnf
Connect Confirm
ack
time-out
Transfer
DATA (0)
k
k
k
sm_message.cnf
ACK (1)
DATA (1)
ACK (2)
v
alive
v time-out
v
DATA ( last)
sm_message_ind
ACK (last)
Disconnection
v late
acks
A transport exchange consists of three phases: connection, transfer and disconnection
In this example, the transfer takes place with a window size of 1
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Real-Time Protocols
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Session: Call And Reply Over A Network
application
process
Vehicle
Bus
Train
Bus
Call_request
Vehicle
Bus
application
process
connect
confirm
data
messenger
Call
Phase
Receive_request
router
router
connect
messenger
connect
request
Receive_confirm
data
ack
server
works
Reply
Phase
Call_confirm
messenger
Reply_request
router
connect
confirm
router
replier
time-out
messenger
connect
request
connect
time
data
data
ack
Reply_confirm
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Software Structure
1. General Principles
2. Variables
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
3. Message Data
1. Principle of Message Data communication
2. Link Layer Interface
3. Networking and Routing
4. Transport and Session Layer
5. Software structure
6. Application Interface
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Software: Message Software Structure
Application
Process 1
Application
Process 2
Application
Process 3
Application
Process n
AMA
AMA
AMA
AMA
Application
Message
Interface
MAA
Function Directory
Station Directory
MAA
MAA
Session Layer
transport
transport
network
Transporttransport
Layer network
Network network
Layer MLA
MLA
MLA
MLA
MLA
MLA
MLA
MLA
Messenger
Process
Instances
Link Interface
Link Processes
LMA
LMA
Link 1
Link 2
for router
station only
Bus 2
Bus 1
Applications access the network through the Application-Message Interface (AMI)
This interface supports multiple simultaneous calls and replies
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Software Interfaces
Application
Message Data
Interface
Process Data
Interface
Kernel
Messenger
Link Layer
Physical Layer
Interface
Physical Layer
Porting of the TCN software to different platforms is eased by well-defined interfaces
between the communication software and the application, the kernel and the link layer.
The bus-specific link layer also has a defined interface to the physical layer.
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Processor Interface Library (PIL)
The Messenger relies on services of the kernel
(e.g. memory allocation, timers, task wake-up)
To ease portability, the kernel services are defined in an interface
module, the Processor Interface Library (PIL).
The PIL provides a set of basic functions as any commercial kernel
(e.g. VRTX, WinWorks) can deliver.
Writing the PIL module is part of the porting process. In many cases,
the PIL modules consists only of a redefinition of existing functions.
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PIL Functions
Block copy
pi_copy8, pi_copy16
Interrupt Control
pi_disable, pi_enable disables/enables all interrupts
pi_call_hw_int
software trap
Dynamic Memory pi_alloc, pi_free
allocate memory block, free it.
Queues:
pi_create_queue
pi_accept_queue
pi_send_queue
pi_receive_queue
create queue, define priority
check if a mesages is in the queu
insert a message in the queue
suspend until message or time-out
Semaphores
pi_create_semaphore
pi_inquiry_semaphore
pi_pend_semaphore
pi_post_semaphore
create semaphore, define priority
check semaphore value
decrement sema, suspend if 0.
increment semaphore
Tasks
pi_create/delete_task
pi_lock_taks
pi_unlock_taks
pi_create_time-out
pi_enable_time-out
pi_disable_time-out
pi_delete_time-out
not part of PIL
begin critical section
end critical section
define function to call
enable a time-out and specify value
disable time-out
delete time-out
Time-outs
IEC Train Communication Network
Real-Time Protocols
41
1999 December, HK
IEC 61375 - Clause 2
AMI Procedures
Caller Interface
am_call_request
am_call_confirm
am_call_cancel
sends a call message
called on arrival of the reply message (or error)
cancel this call
Replier Interface
am_bind_replier
am_unbind_replier
am_receive_request
am_receive_confirm
am_reply_request
am_reply_confirm
am_receive_cancel
announces the service to the messenger
retires the service
expresses readyness to receive
called on arrival of a call message
sends the reply message
terminates the reply
cancels a receive or an unconfirmed reply
Directories (network layer access)
am_directory_insert
am_directory_remove
IEC Train Communication Network
Real-Time Protocols
inserts an entry in the directory
removes an entry in the directory
42
1999 December, HK
IEC 61375 - Clause 2
IEC Train Communication Network
Real-Time Protocols
43
1999 December, HK
IEC 61375 - Clause 2
IEC Train Communication Network
Real-Time Protocols
44
1999 December, HK
IEC 61375 - Clause 2