Basler Electric DECS-400 - Manual (Page 221)

9369700990 Rev R 209
Loop Back Diagnostic Test (FC=8) with Diagnostic Sub Function, Return Query Data
This query contains data to be returned (looped back) in the response. The response and query message
should be identical. If the query is a broadcast (device address = 0), no response message is returned.
Device
Address
Function
Code =
08 (hex)
Sub-function
High
00
Sub-function
Low
00
Data High
XX
(don’t care)
Data Low
XX
(don’t care)
CRC
Low
CRC
High
Loop Back Diagnostic Test with Diagnostic Sub-Function, Restart Communications
Option
This query causes the DECS-400 remote communication function to restart, terminating an active listen-
only mode of operation. Primary relay operations are not affected. Only the remote communication
function is affected. If the query is a broadcast (device address of 0), no response message is returned.
If the DECS-400 receives this query while in the listen-only mode (LOM), no response message is
generated. Otherwise, a response message identical to the query message is transmitted prior to the
communication restart.
Device
Address
Function
Code =
08 (hex)
Sub-function
High
00
Sub-function
Low
01
Data High
XX
(don’t care)
Data Low
XX
(don’t care)
CRC
Low
CRC
High
Loop Back Diagnostic Test with Diagnostic Sub-Function, Force Slave to Listen-Only
Mode
This query forces the addressed DECS-400 to the listen-only mode for Modbus communication, isolating
it from other devices on the network.
While in Listen mode (LOM), received data is monitored but no responses are transmitted. The only query
that will be recognized and processed while in LOM is a maintenance restart command (Function Code 8,
Diagnostic Code 1).
When the DECS-400 receives the restart communication query, the listen-only mode is removed.
Device
Address
Function
Code =
08 (hex)
Sub-function
High
00
Sub-function
Low
04
Data High
XX
(don’t care)
Data Low
XX
(don’t care)
CRC
Low
CRC
High
Data Formats
DECS-400 data does not need to be converted into any special format for transmission over a Modbus
network.
Modbus registers hold original DECS-400 data of the generic (built-in) data types listed in Table 28.
Table 28. Generic Data Types and Description
Generic
Data
Types
Corresponding built-in data
type (Storage Format) Data Range
Data
Size
in
bytes
Total number
of Modbus
Registers to
hold data
UI8 UCHAR: unsigned character 0 to 255 1 1
UI6 UINT16: unsigned short integer 0 to 65,535 2 1
UI32 UINT32: unsigned long integer 0 to 4,294,967,295 4 2
I8 CHAR: signed character -128 to 127 1 1
I16 INT16: signed short integer -32,768 to 32,767 2 1
I32 INT32: signed long integer -2,147,483,648 to
2,147,483,647 4 2
R32_23 FLOAT: floating point number Approximately 8.43 x 10
-37
to
3.38 x 10
38
4 2
DECS-400 Modbus™ Communication