semaphore TBOX LT2-530 Series, Руководство пользователя, Страница: 139 / 197

Version : 1.09 139
15.3. ModBus Transactions through modem
With a remote device accessed by a dial-up modem, the connection must be first established using an
Alarm “ModBus”.
The sequence is the following:

Create a Remote Device, associated to the communication port of the modem and to a Trigger – DIV
(digital register) always active.

Create the ModBus Transactions associated to this device.

Create an Alarm Recipient of type ‘ModBus - Master’, with the telephone number of the remote device.

Create an Alarm Condition, associated to the event requiring communication with the Remote TBox and
to the Recipient created above.

When TBox needs to communicate, generate the alarm condition.

When modems are connected
(can be checked using the communication variable DCV – Comx.Call)
and Trigger is active (see above) ModBus Transactions associated to this station will be executed.

Acknowledge the alarm, for instance using the special analog variable ‘AlaRec’. You write into ‘AlaRec’
the ID of the “ModBus-Master” recipient.

Stop connection by writing ‘0’ to the Communication Variable ‘COMx.HookLink’, alternatively,
communication will be automatically stopped after 1 minute (see hangup timeout below).
15.4. Timing configuration of ModBus Transactions
Several timings can be adjusted when communicating through ModBus Transactions. Their value mostly
depends on the media and the baudrate (see on line help for more info).
They are available from the tab ‘Advanced’ of the properties of the communication port.
Example with RS485 of the CPU
Packet reception delay: maximum time for
receiving a valid frame.
ModBus Master Properties
timeout: maximum time to receive an answer
before sending the next query
Number of Tries: in case of error, number of times
a query is sent
Interframe gap: after having received a valid
answer, time before sending the next query.
Hang up timeout: doing a ModBus Master define
the maximum connection time. The maximum
value is 600 seconds.
Value=0 means it will never hang up!
ModBus Slave Properties
Interframe gap: after having received a valid
request, time before sending the answer.