Micromod MOD: Modcell 2050R MODBUS Communications - Manual (Page 31)

IB-23C650M
BASIC OPERATION WITH A HOST DEVICE
BASIC OPERATION WITH A HOST DEVICE
This section supplements the Basic Operation Section in IB-23C650.
It covers the operational activities related to Modbus communication
which are performed in the DISPLAYS MENU.
Enabling Write Communication With a Host
After completing the RS-485 communications setup, the host can read
instrument data when the bus is enabled (see Table 1, Step 9). If write
communication is required and the communication mode is LOCKED,
the write function can be enabled as follows:
1. Go to the DISPLAYS MENU.
2. Press scroll. This allows the
computer activity status to be
displayed in the DISPLAYS
MENU.
3 Press scroll until CMP appears
in the bottom status display
location.
4. Press DN or UP key to initiate
communication with the host.
When the key is pressed, the
engineering display reads
REQUESTD for a few seconds,
then changes to ENABLED.
Standard Communication With a Host
In the standard communications mode the instrument functions as a
stand alone controller which can receive read and write commands from
the host. In this mode the last attribute entry becomes the active entry.
For example, if the operator sets an active set-point value via the
instrument display, and moments later the host sends a new set-point
value, the controller uses the operators value until it receives the host
value. At that time the host value becomes the new active set-point.
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