Eaton MTL83*C Modbus Software Manual

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Eaton MTL83*C Modbus Software Manual Manual pdf 9 page image

5INM MTL83xC PC Modbus Rev 1DRAFT - 06 January 20193 6 Interconnection of the MTL838CThe MTL838C may be connected to a Modbus host in a number of ways.Two RS485 outputs, Link 1 and Link 2, are provided on the MTL838C. As there aretwo outputs the unit can either be connected to a single Modbus master, with dualredundancy, or connected to two separate Modbus hosts.The MTL838C will respond on whichever RS485 connection the query is received,and there is no restriction placed on the simultaneous use of both interfaces. TheModbus addresses for each Link may only be set by using the PC software.3 7 Initialization modeThe MTL838C has two distinct modes of operation - normal and initialization.It will always enter initialization mode during power-up. It can also be triggered bythe detection of internal hardware or software faults, or after receiving an instructionfrom the host to reset some or all of the configuration registers.During initialization, the unit will ignore all commands from the master.The initialization period will take several seconds to complete all the necessaryoperations and calculations. Following successful initialization, the unit willautomatically enter, or return to, normal operation mode.If a corrupted configuration database is detected during initialization the unit willrevert to a set of default values, and on entering normal operation mode, will issueexception responses when requested by the host to read input values. Exceptionresponses will continue to be issued until the unit is re-configured. The need to re-configure the unit will remain even if the MTL838C is powered down and back up.If a corrupted configuration is detected, the slave address may be reset. If thisoccurs, the user must use the PC software to set the slave address.Also, when the PC software is communicating with the MTL838C, Modbuscommunications are disabled. This is to prevent the possibility of writing to theconfiguration database simultaneously from two sources.3 8 Slave, Transmitter and Input addressingThe following discusses the allocation of addresses to the slaves on the Modbusnetwork - including the MTL838C - and the allocation of addresses for thetransmitters and inputs connected to each MTL838C.3 8 1 Addressing MTL838C slavesModbus allows slave addresses in the range 1 to 247. JBUS allows slave addressesin the range 1 to 255. This is the only difference between the two protocols. TheMTL838C will accept addresses in the range 1 to 255 for each Link. Care should betaken when setting the addresses for each Link using the PC software. For example,if both Links are connected to the same Host, the addresses should probably bedifferent.The Modbus address for each MTL838C slave is set via the PC software. Forreasons of security, it is not possible to set the address of the slave via theModbus host.