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MX/DDC-100 Field Unit Installation and Maintenance FCD LMENIM2329-01 – 03/11
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Message Breakdown
Query Response
7D Slave (Field Unit) Address 7D Slave (Field Unit) Address
03 Function 03 Function
00 Starting Address Hi 06 Byte Count
07 Starting Address Lo 00 Data Hi (Register 40008)
00 No. of Points Hi 3D
1
Data Lo (Register 40008)
03 No. of Points Lo 08 Data Hi (Register 40009)
BFF6 Error Check (CRC) 44
2
Data Lo (Register 40009)
00 Data Hi (Register 40010)
00 Data Lo (Register 40010)
3E07 Error Check (CRC)
Note 1: 003Dh equals 61 Decimal (actuator Analog Input 1 in percent format).
Note 2: 0844h equals 2116 Decimal or 0000 1000 0100 0100 Binary (actuator stopped between limits,
local mode, and Channel B Fail bit is ON).
2.3.6 Modbus Function Code 04 (Read Input Register)
This function code is used to read the binary contents of input registers in the DDC-100 Field Unit. The typical use
of this function code is to read the analog input registers. If the field unit is configured for scaled analog data, the
register information will be returned as a percent from 0 to 100 (see NOTE below). The first analog input register
(Analog 4) will start at register 30005 through (Analog 1) Input Register 30008.
This function code may also be used to read the information available in registers 9 through 16.
NOTE: Limitorque field units can be configured to report analog data in several formats. See the appropriate field unit
manual for details.
Example
Poll field unit number 70 for 4 registers starting at register 5 (Analog Input Registers 1-4).
(This example assumes that the field unit is configured for scaled analog data.)
Query: 460400040004BF7F
Response: 460408FFFFFFFF002B001EDBA8
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