Bronkhorst EL-FLOW Base 2014 - Manual (Page 19)

BRONKHORST HIGH-TECH
More detailed information about Modbus can be found at http://www.modbus.org or any website of
the (local) Modbus organisation of your country (when available).
3.4.3 Response time
This slave device will respond on each valid request from the master within 100 msec. This means that
the response timeout setting of the master should be set to a value larger than or equal to 100 ms.
3.4.4 Supported Modbus functions
This section describes the supported Modbus function codes. Refer to document [1] “MODBUS
Application Protocol Specification V1.1b, December 28, 2006” for more details.
More detailed information about Modbus can be found at http://www.modbus.org or any website of
the (local) Modbus organisation of your country (when available).
Read Holding Registers (03)
Possible exception responses:
• 02, ILLEGAL DATA ADDRESS, in case of reading of non-existing address, or reading a part of a
multiregister parameter (float, long, etc)
• 03, ILLEGAL DATA VALUE, in case of reading less than 1 or more than 125 registers
• 04, SLAVE DEVICE FAILURE, in case of reading a write-only register
!
The maximum message size for the Read Holding Registers function is 100 bytes at 9600 baud (200
bytes at 19200 baud and 400 bytes at 38400 baud). When this size is exceeded, corrupted responses
may be received.
Write Single Register (06)
Possible exception responses:
• 02, ILLEGAL DATA ADDRESS, in case of writing to non-existing address, or writing to a part of a
multiregister parameter (float, long, etc)
• 04, SLAVE DEVICE FAILURE, in case of writing to read-only register
• 04, SLAVE DEVICE FAILURE, in case of writing illegal value to register
Write Multiple Registers (16)
Possible exception responses:
• 02, ILLEGAL DATA ADDRESS, in case of writing to non-existing address, or writing to a part of a
multiregister parameter (float, long, etc)
• 03, ILLEGAL DATA VALUE, in case of reading less than 1 or more than 123 registers
• 04, SLAVE DEVICE FAILURE, in case of writing to read-only register
• 04, SLAVE DEVICE FAILURE, in case of writing illegal value to register
When one of the written registers raises an exception, the value written to all subsequent registers are
discarded (ignored).
Parameter Options Remarks
Addressing address configurable from 1 to 247
(default 1)
see section 3.4.1
broadcast support Yes
baud rate 9600, 19200 (default), 38400 see section 3.4.1
parity None, Odd, Even (default) see section 3.4.1
transmission mode RTU/ASCII Auto detection
data bits RTU=8, ASCII=7 not configurable
electrical interface RS485 2W-cabling See document:
9.16.091 - Hook-up diagram EL-FLOW Base
connector type DB9 Male See document:
9.16.091 - Hook-up diagram EL-FLOW Base
9.17.061 EL-FLOW Base Series Mass Flow Controllers Page 19