Thermo Scientific APEX 100, User Manual

Page: 352 / 442

Page 352
Thermo Scientific APEX User’s Guide
Read Data
When the master wants to read a parameter, it simply reads the appropriate register or
registers. Using the standard commands of the Modbus TCP, it is possible to read all the
data of the table.
Write Data
Each parameter that can be modified by the master, has two control bits to perform the
handshaking operation, which are implemented as coils. These two control bits are
named as follows.
Control bit Description
Parameter-change notification Used to notify the APEX that the master
has modified a parameter.
Parameter-change acknowledge Used to acknowledge that the APEX has
processed the parameter change.
If the master wants to change a parameter, it first updates the appropriate registers and
then notifies the APEX by toggling the corresponding “parameter-change notification”
coil. When the APEX has processed this change, it toggles the corresponding
“parameter-change acknowledge” coil to signal that the parameter change has been
processed.
If the parameter written by the master is outside the range of acceptable values, then
the APEX will not use it and will continue to use the previous value. In this case the Read
and Write registers will contain different values, but the Read register will always contain
the current value being used by the APEX. Note that the “parameter-change
acknowledge” coil will still be toggled, indicating that the APEX has processed it.