Flowserve MX-100 Field Unit - Manual (Page 14)

MX/DDC-100 Field Unit Installation and Maintenance FCD LMENIM2329-01 – 03/11
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2.3.2 Modbus Function Codes
The controlling device (master) must conform to the Modbus protocol as defined in the Modbus-IDA Modbus
Application Protocol Specification V1.1a (http://www.Modbus-IDA.org) and support Modbus function codes 01
through 06, 08, 15, and 16. These function codes are a subset of the complete protocol and are defined in Table 2.1.
Table 2.1 – Modbus function codes supported
Extended
Function Bit/Register Addressing
Code Name Addressing Range
01 Read Coil Status Bit 0,000 - 9,999
02 Read Discrete Inputs Bit 10.000 - 19,999
03 Read Holding Register Register 40,000 - 49,999
04 Read Input Register Register 30,000 - 39,999
05 Force Single Coil Bit 0,000 - 9,999
06 Preset Single Register Register 40,000 - 49,999
08 Diagnostics N/A N/A
15 Force Multiple Coils Bit 0,000 - 9,999
16 Preset Multiple Registers Register 40,000 - 49,999
See Table 2.2 for a complete listing of MX/DDC holding registers.
2.3.3 Modbus Function Code 01 (Read Coil Status)
This function code is used to read the coil status in the DDC-100 Field Unit. There are nine coils available to be read
on DDC-100 Field Units as shown in Table 2.2. For the MX/DDC, Coil 1 indicates CLOSE contactor and is interlocked
with Coil 2, Coil 2 indicates OPEN contactor and is interlocked with Coil 1. When the I/O Module is used in non-MOV
(motor-operated valve) mode, relays 1 through 6 or coils 3 through 8 are available for user configuration.
Table 2.2 – DDC-100 coil assignments, Modbus 05 command usage for digital outputs
Coil Number Bit Number Function
1 00 Close/Stop
2 01 Open/Stop
3 02 S1 or R1 (Opt) Latched
4 03 S2 or R2 (Opt) Latched
5 04 R3 (Opt) Latched
6 05 R4 (Opt) Latched
7 06 R5 (Opt) Latched
8 07 R6 (Opt) Latched
9 08 R7 (Opt) Latched
10 09 R8 (Opt) Latched
The normal response to the (05) command is an echo of the command.
Example
Poll field unit number 3 for 8 coils starting at coil 1.
Query: 0301000000083C2E
Response: 03010118503A