BusWork® 965EN Module User’s Manual Modbus TCP/IP mV/TC Input
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Acromag, Inc. Tel:248-295-0880 Fax:248-624-9234 Email:
30
Below is a subset of standard Modbus functions that are supported by this
module along with the reference register addresses that the function
operates on. Use these functions to access these registers as outlined in
the Register Map for sending and retrieving data.
The following Modbus functions operate on register map registers to
monitor, configure, and control module I/O:
CODE
FUNCTION
REFERENCE
01 (01H)
Read Coil (Output) Status
0xxxx
02 (02H)
Read Input Status
1xxxx
03 (03H)
Read Holding Registers
4xxxx
04 (04H)
Read Input Registers
3xxxx
05 (05H)
Force Single Coil (Output)
0xxxx
06 (06H)
Preset Single Register
4xxxx
15 (0FH)
Force Multiple Coils (Outputs)
0xxxx
16 (10H)
Preset Multiple Registers
4xxxx
17 (11H)
Report Slave ID (See Below)
Hidden
If an unsupported function code is sent to a module, exception code 01
(Illegal Function) will be returned in the response. If a holding register is
written with an invalid value, exception code 03 (Illegal Data Value) will be
returned in the response message. You may refer to the Modbus
specification for a complete list of possible error codes.
965EN-4006 Report Slave ID Example Response
FIELD
DESCRIPTION
Unit ID
Echo Unit ID Sent In Query
Function Code
11
Byte Count
42
Slave ID (Model No.) 04=965EN-4004 (4 mV/TC Input)
05=965EN-4006 (6 mV/TC Input)
Run Indicator Status
FFH (ON)
Firmware Number
String (Additional
Data Field)
41 43 52 4F 4D 41 47 2C 39 33 30 30 2D
31 32 33
2C 39
36 35
45 4E 2D
34 30 30 36
2C
30 31 32 33 34 35
41
2C
30 31 32 33 34 35
(“ACROMAG,9300-
123
,9
65
EN-
4006
,
serial
number&rev
,
six-byteMACID
”)
For detailed information on Modbus, feel free to download technical
reference 8500-648,
. For
more information on Modbus TCP/IP, download whitepaper 8500-765,
“Introduction To Modbus TCP/IP”.
For your convenience, 9xxEN Ethernet modules mirror the contents and
operation of registers 0xxxx, 1xxxx, & 3xxxx (as applicable) into holding
register space for systems and controllers that cannot directly access
registers 0xxxx, 1xxxx, & 3xxxx.
All Modbus registers of this model can now be written to, or read from, using
either the standard methods described in the Modbus specification, or
through mapping (mirroring) to the Holding Registers. The registers are
mapped as follows and specifics follow the mapping:
Register Functions
IMPORTANT: When using
your own software to
manipulate the module, please
note that the maximum query
through the Modbus TCP
interface is only 50 registers,
due to the maximum buffer
size limitations of the TCP/IP
stack. As such, you can only
request data from 50 registers
at one time for commands that
access multiple registers. For
example, the Read Holding
Registers command may only
retrieve the contents of
registers 40001 to 40051 in
one read.
Register Mirroring
