Series 2000 Communications Handbook - Soliton

Modbus & EI Bisynch AddressesSeries 2000 Communications Handbook5. Chapter 5 Modbus and EIBisynch Addresses5.1. INTRODUCTIONThis section of the manual provides a list of all parameters in 2200 and 2400 seriescontrollers that are available over the communications link. As far as possible, it follows thesame organisation as the controller user interface itself. Definitions of parameters and statusinformation not available via the controller display are also provided.All 2000 Series controllers may be configured for a wide variety of functions and someparameters will only be available if the related function is configured. Modbus addresses thatare not supported have no parameter assigned. In normal operating mode all configurationparameters are read only. To be able to write to these parameters, the controller must be inconfiguration mode.If the Modbus protocol is used to read a parameter that is not configured, an undefined valuewill be returned. The EI-Bisynch protocol will return an EOT character to signal that theparameter is not available.Modbus function 6 single parameter write operations to unconfigured or read only parameterswill be rejected with a Modbus ‘data error’ return code. The EI-Bisynch protocol rejects suchrequests with the NAK character.NB: Blocks of data written using Modbus function 16 containing values in positionscorresponding to the addresses of unconfigured parameters are not generally rejected,although the values of any unconfigured parameters are discarded. This allows relativelylarge blocks of parameter data to be written in a single operation, even if the block containsa little ‘empty’ space. This is particularly useful for operations such as ramp/dwell programdownloading, recipes, or instrument cloning. However this also leads to a potential pitfall: ifthe block of data contains only a single parameter, and the destination address refers to anunconfigured or unused Modbus address, the write operation will appear to be successful,although the controller will have discarded the value.Attempts to write to read only parameters over Modbus, even when they are embedded withina block of data, will be rejected with a Modbus ‘data error’. Any subsequent values in theblock will also be discarded.Rules for read and write operation in the Modbus IEEE area are dealt with in Chapter 3.5.2. MODBUS AND BISYNCH ADDRESSES.This section of the manual provides a list of all parameters in 2200 and 2400 seriescontrollers that are available over the communications link. As far as possible, it follows thesame organisation as the instrument user interface itself. Definitions of parameters and statusinformation not available via the instrument display are also provided.5-2 Series 2000 Communications Handbook Part No HA026230 Issue 2.0 Feb-00