IFM AL1940, Device Manual

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ifm Device Manual IO-Link Master with Modbus interface CabinetLine 8 Ports IP 20 (AL1940) 05 / 2018
Configuration Modbus
>
8.3.11 Modbus: Programmers' notes
Rules for accessing the Modbus register ...............................................................................................58
Supported function codes .......................................................................................................................59
Use acyclic services ...............................................................................................................................59
17965
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Rules for accessing the Modbus register
13916
The Modbus table of the AL1940 is subdivided into areas.
1
A register area has one
start address.
2
A register area consists of
one or several registers
(length/number of words)
The following general rules apply for access to the Modbus registers:
► Only read or write Modbus registers word by word.
► Only use the valid function codes to read or write Modbus registers (→
Supported function codes
(
→ p.
59 )).
► Only implement read and write access via valid start addresses. Access via an invalid start
address generates an error.
Example:
Task: Write IO-Link output data of the IO-Link port X02 (process data length n = 2 bytes)
Solutions:
Right:

Version 1: "Output Data" area (
→ Output Data
(
→ p.
81 ))
► In the Compact Output Block of the ports X01…X04, read the registers 600…603 (FC03, start
address: 600, length: 4 words)
► Change read values of the register 601.
► In the Compact Output Block of the ports X01…X04, write the registers 600…603 (FC16, start
address: 600, length: 4 words)

Version 2: "Single Port Access" area (
→
Single Port Access
(
→ p.
82 ))
► Write the required value into register 2101 (FC06, start address: 2101)
Wrong:
► In the Compact Output Block of the ports X01…X04, write the register 601 (FC06, start
address: 601, length: 1 word)