Modbus Protocol; Table 4: Region 9: 3120 Unit Registers - Sensor Electronics SEC Millenium Series Instruction And Operation Manual

Holding Read or
Register Write
Address
42x28 -x 30 Read/Write Calibration Value (IEEE 754 32-bit float)
42x31 -x32 Read
42x33 Read
42x34 - x37 Read
42x38 - x39 Read
42x40 Write Only Start Self Test (with password)

Table 4: Region 9: 3120 Unit Registers

Holding Read or
Register Write
Address
42901 Read
42902 - 03 Read
42904 - 05 Read
42906 - 11 Read
42912 - 17 Write Only Clock Write Registers (New write hold registers)
42918 Write Only Set Clock from New Clock write hold registers
42919 Write Only Diagnostics (force alarm/fault relays, force LED blinking)
42920 Write Only Set Unit into Listen Only Modbus Mode
42921 Write Only Restore Unit back from Listen Only Modbus Mode
42922 Read
42923 Read
42924 - 25 Read

Modbus Protocol

Introducing Modbus Protocol
Modbus communication is based on a master–slave technique, in which only one
device (the master) can initiate transactions (queries). The other devices (the slaves)
respond by supplying the requested data to the master, or by taking the action requested
in the query. The master can address individual slaves or can initiate a broadcast message
to all slaves. Slaves return a message (a response) to queries that are addressed to them
individually. Responses are not returned to broadcast queries from the master.
The Modbus protocol establishes the format for the master's query by placing the
device (or broadcast) address, a function code defining the requested action, any data to
be sent and an error-checking field into the message. The slave's response message is
also constructed using Modbus protocol. The response contains fields confirming the
action taken, any data to be returned and an error-checking field. If an error occurred in
receipt of the message, or if the slave is unable to perform the requested action, the slave
will construct an error message and send it as the response.
SEC 3120 16-bit Modbus Manual
For Version 1.2 and above
Sensor Register Description
(See Parameter Table for specifics)
Sensor Range (IEEE 754 32-bit float)
Alarm Configuration (bit map)
Gas Name (ASCII characters eight, 1st left to right)
Gas Units Name (ASCII characters four, 1st left to right)
3120 Unit Register Description
(See Parameter Table for specifics)
Unit Operating Status (bit map)
Fault Relay Reason Code (32-bit bit map)
Unit Serial Number (32-bit integer)
Clock Read Registers (real-time)
Maximum number of sensors that can be attached
Unit Type Code
Unit Firmware Version (2- words for major.minor.build)
Page 21 Of 46
December 2012
Sensor Electronics Corporation
P/N 1580282, Rev. 1, 20121228