6720892984 (2019/02) US SSB
72 | Service reminder
K.7 Examples: How to update a register with a Write request via Modbus
K.7.1 Example of a simple Write command
The following example explains how to update a register with a (simple) write request via Modbus:
Address 900PB Command simple write Register to update New value Checksum
01h 06h 01F6h 0262h E8D8h
K.7.2 Example of Command-Sequences for updating the CH setpoint via Modbus
This example explains how to update the CH setpoint from value 60°C to value 61°C in the 900PB Display (Modbus address 01h) and shows the
sequence of Modbus commands that have to be written:
Enable write action Command on modbus Write from … to… *
Enable the control Register (99) by writing value 1 in the register 99. The register
99 will be cleared after 3 sec. from 900PB, therefore the next write command has
to be send within 3 sec.
01h 06h 00h 63h 00h 01h B8h 14h
Modbus-device ¨ 900PB
Ack write enabled Command on modbus Write from … to… *
The ack for the simple write request is the repetition of the previous request
command.
01h 06h 00h 63h 00h 01h B8h 14h
900PB ¨ Modbus Device
Write ch-setpoint value Command on modbus Write from … to… *
Simple Write in register 502 (CH-Setpoint) the value 610. Send a request for
update the CH- Setpoint at a value of 61°C
01h 06h 01h F6h 02h 62h E8h 8Dh
Modbus Device ¨ 900PB
Ack new ch-setpoint value Command on modbus Write from … to… *
The ack for the simple write request is the repetition of the previous request
command
01h 06h 01h F6h 02h 62h E8h 8Dh
900PB ¨ Modbus Device
* Also see the scheme on the following page that shows the different writing actions between the Modbus Device and the 900PB .
The following scheme illustrates the examples from the previous paragraph and shows from which device to (another device) the Writing actions take
place:
Enable write action
Ack write enabled
Write Setpoint value
Ack new setpoint value
900PB
(01h)
Modbus
Device
NOTE: Modbus Interface and Diagnostics software is available via ebm-papst Heating Systems B.V.
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