Series 2000 Communications Handbook - Soliton

Series 2000 Communications HandbookModbus and EIBisynch Advanced Topics7.8.2. ModbusThere are many ways of connecting 2000 Series Instruments to Programmable LogicControllers using Modbus, for example the ProSoft 3100/3150 MCM module for AllenBradley PLC/5 and SLC/5. It is usually best to avoid the use of Basic modules which mayresult in very slow communications. Your supplier will often be able to advise on a solutionfor a particular make of Programmable Logic Controller, but if requesting information fromthird party vendors, note that the 2000 Series supports standard Modbus RTU, allowing useof function 16 for block write operations, and functions 3 and 4 for reads.Because Modbus modules often allow a restricted number of block operations, it issometimes useful to create large blocks containing all the data to be written for a giveninstrument. Because the 2400 contains a mixture of read/write and read-only data, this can bedifficult to achieve. Therefore, for 2400 firmware versions 3.00 and greater, a facility hasbeen provided that allows block writes to continue even if values in the block are notcurrently writeable (the values that are not writeable are ignored, and there is no error return).To switch this facility on, write a value of 1 to the instrument Modbus register 220. Thesetting of this register is held in non-volatile memory and so you only need perform thisoperation once. To cancel the facility, write 0 to register 220.Series 2000 Communications Handbook Part No HA026230 Issue 2.0 Feb-00 7-9