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This command is required since the link end which intents to stop link operation must inform the other end of the link.
Otherwise the link shutdown might be interpreted as a link failure.
If a link has been shut down previously, it can be requested to start up again by a 'restart link operation' complex command.
This command has to be issued via an already operating link to the CPU of a node which then initiates the actual restart
operation for the link requested to start up.
Details of the link shutdown operation are given in para. 4.
Note that the simple procedures work only for direct connected systems but that systems incorporating a router require more
complicated procedures, e.g by involving the system controller.
All complex control commands should be addressed. This means that a complex control command received via one link
interface can control every other link interface on the same node.
13.4 Procedure Rules
13.4.1
Acknowledgements
Data Transmission and Simple Commands
With the exception of the reset command, the reception of each packet is acknowledged by an acknowledge packet. The
acknowledge packet informs the requester node on the successful reception of the packet but does not contain information
about a completed execution of a command. The acknowledgement covers
-
in case of data transfer commands (including encapsulated complex commands) the correct reception of the packet
including the associated EOP marker and the forwarding of the data to the receive FIFO in the link interface. It does
not cover any operation related to memory access of the node CPU's working (communication) memory.
-
in case of simple commands the correct reception of the packet including the associated EOP marker, the successful
decoding of the command and the forwarding of the command to the command execution unit. The
acknowledgement covers additionally the cases whether or not the command execution unit has been enabled
previously for safety critical commands or not.
In case of data transmission or transmission of simple commands, the requesting node has to wait for the last acknowledge of
a previous data transmission or the acknowledge of a previous simple command execution request or the high level
acknowledge of a previous complex command before a new simple command execution request packet can be send. In other
words: split transactions are NOT allowed.
Within this protocol only two forms of acknowledgement are required:
-
reception successful
-
reception with errors or problems with the execution of the requested command
If the second form of the acknowledgement is received, it is up to the requester node to read the status register of the
responder node in order get more information about the malfunction.
The acknowledge packet structure is defined in para. 5. The acknowledge packet is generated immediately after the reception
of the 'end of packet' marker of the received packet and forwarded to the transmission segment of the link channel. If data
and acknowledge packets compete on access to the transmission segment, acknowledge packets have precedence but can
occupy the transmission segment only after the previous transmission has been finished. Since a currently running
transmission cannot be interrupted, a significant delay between end of the received packet and transmission of the
acknowledgement can occur.
SMCS332SpW
User Manual
– All Rights Reserved – Copyright per DIN 34 –
EADS Astrium GmbH, ASE2
Doc No: SMCS_ASTD_UM_100
Issue:
1.4
Updated: 9-Sep-2006
Page:
118 of 131
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