MVI56E-MNETC/MNETCXT ♦ ControlLogix Platform Reference
Modbus TCP/IP Client Enhanced Communication Module - Client/Server User Manual
ProSoft Technology, Inc. Page 109 of 172
September 20, 2018
The following illustrations show the effect of changing the value of the Select
Priority Read Block register (Write Block offset 247). In the following histogram
curve, the Select Priority Read Block is equal to 0.
Local:1.O.Data[247] = Select Priority Read Block.
Local:1.I.Data[249] = Read Block ID.
In the example above, all read blocks (1 to 10) are returned in sequential order.
Select Priority Read Block = 5
If the ladder logic changes the value of Local:1:O.Data[247] from 0 to 5, note that
the Local:1:I.Data[249] value begins to alternate between Block IDs 5 and 6 as
long as Local:1:I.Data[247] stays set to 5.
5-6-5-6-5-6-5-6-5-6-…
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