ProSoft Technology 5201-MNET-101S - Manual (Page 115)

IEC-101 Slave ♦ ProLinx Communication Gateway Reference
IEC 60870-5-101 v3 Slave (Firmware version 3.xx) Protocol Manual
ProSoft Technology, Inc. Page 115 of 159
August 6, 2010
General Command Block Structure
A command request block will have the following general structure. The
command request block should be copied starting at the database address given
by the configuration parameter DB Input Window Start:
Word Offset Description
0 Block ID1 - Command Request Without Response
1 Block ID2 - Command Request With Response
2 to 98 Command Request Data
99 Block ID1 - Command Request Without Response
Where:

Command Request Without Response Block is transferred from the remote
node to the ProLinx gateway to request a special task that does not require
data back from the gateway. For example, a Set Time command block sets
the gateway time but does not require data back from the gateway.
 Command Request With Response Block requires data back from the
gateway. The response block is copied at a different database area. For
example, a Get Time command block requests the gateway time information.
So a command block may:

Perform command request without response only
 Perform command request with response only
 Perform both command request with response and command request without
response
The ProLinx gateway recognizes a new block command request if:

A new command request block ID is received at word offsets 0 and 99
 The same command request block ID is received at word offsets 0 and 99
If these conditions are fulfilled the gateway will process the request and response
command blocks.
Once the command response block is processed, the response data will be
copied to the ProLinx database with the following structure. The command
response block will be copied starting at the database address given by the
configuration parameter DB Output Window Start:
Word Offset Description
0 Block ID2 - Command Request With Response
1 Block ID1 - Command Request Without Response
2 to 98 Command Response Data
99 Block ID2 - Command Request With Response
The remote node must therefore read this block from the ProLinx gateway to
retrieve the command block response.