Protocol responsibilities, Soe over modbus service responsibilities, Trusted – Rockwell Automation T8xxx Trusted Communications Interface User Manual
Page 65: Communication interface t8151b
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TM
Communication Interface T8151B
Issue 21 Apr 10
PD-T8151B
65
HEADER
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RESERVED
REASON
RESERVED
TYPE
Bit-Field
Description
REASON
Not valid for Variable blocks.
TYPE
1 = Time-stamp block.
2 = Variable block.
Table 32 Variable HEADER field
The ADDRESS field contains the Modbus address of the variable that has changed.
ADDRESS
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ADDRESS
Bit-Field
Description
ADDRESS
The Modbus address of the variable.
Table 33 Variable ADDRESS field
The VALUE field contains the new value of the variable after the change. For Boolean type variables,
the value will be limited to 0 or 1.
VALUE
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VALUE
Bit-Field
Description
VALUE
The new value of the variable.
Table 34 Variable VALUE field
7.3. Protocol Responsibilities
The goal of the SOE Over Modbus protocol is to facilitate the transfer of buffered event data across a
Modbus link. To that end, the protocol establishes well defined register locations as described above.
In addition to the register definitions, the protocol also requires specific sequences of interaction
between the Modbus master (the “master”) and the SOE Over Modbus service (the “service”).
7.4. SOE Over Modbus Service Responsibilities
The sequence begins in the IDLE state. The IDLE state is characterised by the SEQ_NO and
ACK_SEQ being equal, and the NUM_BLKS and ACK_BLKS being equal. On startup, the service will
ensure the registers are initialised to the IDLE state.