Balluff BIS M-370-000-A02, Manual, Page: 110 / 198

MODBUS TCP INTERFACE
103
6
NOTE
NOTE
: when the Node Input Page’s value at register 40001 is returned to
0x0000, the host can assume that the command was at least received and
execution was attempted. The host can also assume that it is OK to clear the
remaining holding registers and write another command to the Device ID
(Node Input Page).
4. After the BIS M-626_ 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 BIS M-626_ 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 BIS M-
626_ 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.