7 Modbus RTU7.4 Operating mode Modbus RTU120 DE1 variable speed starter 09/14 MN040011EN www.eaton.com7.4.2 Structure of a slave response7.4.2.1 Required transfer time• The time between receiving a request from the master and the responseof the DE1 variable speed starter is at least 3.5 characters (idle period).• Once the master has received a response from the variable speedstarter, it must wait for at least the idle period before it can send a newrequest.7.4.2.2 Normal slave response• If the master request contains a write register function (functioncode 06), the variable speed starter immediately returns the request as aresponse.• If the master request contains a read register function (functioncode 03), the variable speed starter returns the read data with the slaveaddress and the function code as a response.7.4.2.3 No slave responseIn the following cases, the DE1 variable speed starter ignores the requestand does not send a reply:• on receiving a broadcast request.• if the request contains a transmission error.• If the slave address in the request does not match that of the variablespeed starter.• With a CRC or parity error.• If the time interval between the messages is lessthan 3.5. characters.￫ The master must be programmed to repeat the request if itdoes not receive a response within a specified time.
