EQJW145: Heating controller
Communication functions
7010015003 A
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© Fr. Sauter AG
6.3
Modbus communication
The EQJW 145 can respond to enquiries in the Modbus RTU protocol as a
slave. For this purpose, an RS-485 two-wire bus is connected to terminals 18
and 19. A suitable Modbus master (BMS centre) can send enquiries or
commands via this bus. Up to 247 devices can be addressed in a
communication network based on the Modbus RTU protocol via an RS485
interface. Up to 32 devices can be connected within a bus segment.
To enable the function, CP02 must be set to 2 (see Section 3.2.4). A unique
address must be assigned at CP05 and the transmission speed (Baud rate)
must be selected with CP03. The data format supported by the controller is
8n1, i.e. the data format comprises 8 data bits, no parity bits and one stop bit.
The following commands are supported:
___________________________________________________________________
Read Coil:
AA 01 XX XX 00 01 CC CC
-- -- ----- ----- -----
Coils =
Adr RC CoilNr Coils CRC
Number of coils to be read
Response:
AA 01 01 YY CC CC
-- -- -- -- -----
Anz =
Adr RC Anz Dat CRC
Number of following data bytes
___________________________________________________________________
Read Holding:
AA 03 XX XX 00 01 CC CC
-- -- ----- ----- -----
Reg. =
Adr RH HR-Nr Reg. CRC
Number of registers to be read
Response:
AA 03 02 XX XX CC CC
-- -- -- ----- -----
Anz =
Adr RH Anz Daten CRC
Number of following data bytes
___________________________________________________________________
Set Coil:
AA 05 XX XX YY 00 CC CC
YY = 0xFF to set,
-- -- ----- ----- -----
0x00 to delete
Adr SC CoilNr Data CRC
(Response identical)
___________________________________________________________________
Set Holding:
AA 06 XX XX YY YY CC CC
-- -- ----- ----- -----
Adr SH HR-Nr Data CRC
(Response identical)
___________________________________________________________________
Fig. 6: Modbus communication-commandos
Current measured values and operating statuses (for example) can be read
out via Modbus. The controller outputs can be switched. The list of the
available data points is given in the Annexe, Section 6.3.1.
If desired, the controller will monitor the activity of the Modbus interface. As
long as valid Modbus enquiries are registered regularly, the controller will reset
the time monitoring. If no more enquiries are directed to the controller for 30
minutes, it will operate independently again. Changes to the controller outputs
triggered via Modbus then become invalid. This function can be disabled with
CP27.
Содержание EQJW145
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