Rockwell Automation T8xxx Trusted Communications Interface - Manual (Page 61)

Trusted
TM
Communication Interface T8151B
Issue 21 Apr 10 PD-T8151B 61
7. SOE Over Modbus Protocol
The SOE Over Modbus Protocol is defined in two parts: the definition of the Modbus registers within
the SOE Address Window, and the defined interaction between the Modbus master and the SOE Over
Modbus service.
7.1. SOE Address Window
The SOE Over Modbus protocol operates over the Modbus addresses within the configured SOE
Address Window. Modbus operations on address within this window are used exclusively for the
protocol. The SOE Over Modbus service defines registers within the address space required for the
operation of the protocol. Each register is accessed in the normal manner (i.e. Modbus reads/writes).
Name Access Offset Length Description
ACK_SEQ Read /
Write Base + 0 1 Acknowledge sequence number
Modbus master writes the sequence number
from SEQ_NO into this register after it has
retrieved the events.
ACK_BLKS Read /
Write Base + 1 1 Acknowledge number of data blocks
Modbus master writes the total number of data
blocks read into this register after it has retrieved
the data.
SYNC Read
Only Base + 2 2 Used internally by the SOE Over Modbus service
to synchronize presentation of event data in a
redundant, fail-over configuration.
LEN_SOE Read
Only Base + 4 1 Length of SOE_DATA area
Contains size of SOE_DATA in words. Note that
this number should be a multiple of four.
SEQ_NO Read
Only Base + 5 1 Sequence Number
Incremented by the service when new event data
is available.
NUM_BLK
S Read
Only Base + 6 1 Number of data blocks
Specifies the number of data blocks available in
the SOE_DATA buffer.
SOE_DAT
A Read
Only Base + 7 Number
of Event
Blocks * 4
SOE data area
Contains time-stamp and event data blocks.
Each block spans four Modbus registers.
Table 24 - SOE Address Window