Filter
Top Products
76 Micro Motion 7829 Viscomaster
®
and Viscomaster Dynamic
™
Viscosity Meters
Modbus Communications
D.5.10 Line dynamic viscosity units
Used in Register 421.
D.6 Establishing Modbus communications
Using ADView, it is possible to establish which devices are available on the network, and their slave
addresses. However, if you are not using ADView, the following procedure can be adopted.
If the meter Slave address or the values of Registers 47 and 48 are not known, Modbus
communications cannot be carried out successfully, and it will be necessary to establish the current
values in these items. The following procedure will do this.
The process is:
1. Find the slave address by trying all possible values until a response is received.
2. Establish whether the register size is 16 or 32 bits by reading register 48.
3. Find the byte order by reading register 47.
Step 1 Find the slave address
Make sure only the meter is connected to the Modbus Master, then send the following message (Read
Register 47):
Wait for a response. If there is none, repeat the same message, with the Slave address changed to 1,
and await a response. Repeat the process until a response is obtained. This will show the slave address
of the meter.
Step 2 Establish register size as 16-Bit versus 32-Bit
Send the following message (Read Register 48), where nn is the meter slave address:
29 20000000 ST_FRAM1_CSF
(1)
FRAM1 CheckSum Fail flag
30 40000000 ST_FRAM0_ACK FRAM0 ACK/data error
31 80000000 ST_FRAM1_ACK
(1)
FRAM1 ACK/data error
(1) The status flags marked thus refer to hardware features not present in the meter. They can safely be ignored.
Index Variable
0cP
1P
2Pas
3mPas
Slave
Address Command
Register
Address Checksum
00 03 00 47
10
00 02 checksum