User's Manual

COBALT UHF-SERIES CHAPTER 7: MODBUS TCP INTERFACE
PAGE 120 OF 140
4.
After the Cobalt executes its given command instructions, it will write the
command response to the holding registers for Device ID 33 (Node Output Page
33). Again, the Overall Length value is written last to holding register 40001.
NOTE: Host-bound data is always written to Device ID 33 (Node Output Page 33).
5.
With holding register 40001 of Device ID 33 (Node Output Page 33) now
containing a non-zero length value, the Cobalt will enable (change from zero to
1) the first bit in the
Output Data Ready Mask.
(The first bit is allocated to Node
Output Page 33).
6.
Once bit 01 in the Output Data Ready Mask becomes enabled, the host retrieves
the data string stored in the holding register area for Device ID 33 (Node Output
Page 33).
7.
After importing the data from Device ID 33 (Node Output Page 33), the host
clears (sets back to 0x0000) the Overall Length value at holding register 40001
of Device ID 33 (Node Output Page 33). In doing so, bit 01 in the Output Data
Ready Mask is also cleared.
NOTE: the clearing of bit 01 in the Output Data Ready Mask indicates to the Cobalt that
the host has received the response and that it is now OK to write another response to
Node Output Page 33.
This completes the Modbus TCP handshaking cycle.