Device Address; Function Codes - JUMO mTRON T Manual

3 Modbus protocol description
3.5

Device address

The device address can be set between 1
cessing unit and each module in the setup program under P
WARE ARRANGEMENT
data exchange options are available for accessing the connected stations.
Query
This is a data request/instruction from the master to a slave via the corresponding device ad-
dress (1 to 254). The slave addressed responds.
Broadcast
The broadcast is an instruction from the master to all slaves via the device address 0 (e.g. for
transmitting a specific value to all slaves).
The connected slaves do not respond. In such a case, the correct acceptance of the value by
the slaves should be checked by a subsequent readout at each individual slave. A data request
with the device address 0 is meaningless.
NOTE!
A maximum of 31 slaves can be accessed via the RS485 interface.
The device address 0 is reserved as a Modbus broadcast address:
an instruction from the master to address 0 is executed by all slaves, however, none of the
slaves respond (since it would otherwise lead to a data collision).
The address is specified in binary format in the transmission protocol.
3.6

Function codes

Function overview
The functions described in the following are available for the readout of measured values, de-
vice and process data as well as for writing specific data.
Function number
0x01 or 0x02
0x03 or 0x04
0x05
0x06
0x10
NOTE!
A hexadecimal number is marked by a preceding "0x".
Example: 0x0010 (= 16
NOTE!
If the central processing unit does not respond to these functions or outputs an error code,
it can be evaluated.
 Chapter 3.9 "Error messages", page 42
28
. Each Modbus station must have a unique device address. The following
Function
Read n bit
Read n words
Write one bit
Write one word
Write n words
)
DEC
and 254 . It is assigned for the central pro-
DEC DEC
ROJECT NAME
Limiting
Max. 256 bits (16 bytes)
Max. 127 words (254 bytes)
Max. 1 bit
Max. 1 word (2 bytes)
Max. 127 words (254 bytes)
> P > H -
ROJECT ARD